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\ the small systems journal 



$2.40 in CANADA 



Jt^ 








MULTI-USER SYSTEM 








■^ 
^ 



OPERATES - Up to 4 terminals running INDEPENDENT programs 
HARDWARE TIME SHARE- Requires no modifications to computer 
IDEAL FOR — All multi-terminal applications 






The SwTPC multi-user system converts our standard 6800 
single user computer into a multi-user time share system 
that may be operated with up to four terminals. The four 
terminals operate independently and may be running four 
different programs. 

No modifications to the computer are necessary, you sim- 
ply plug in the multi-user board and add an interface for 
each additional terminal. 

The multi-user system is ideal for program training, multi- 
station business applications and for computer aided in- 
struction (CAI). Speed reduction from a single user system 
is negligible because all switching is done in hardware. 

Multi-user BASIC, suitable for program instruction and sim- 
ple business applications, is included with the multi-user 



board. An 8K disc BASIC is also available for systems in 
which disc drives are used. This software has a complete 
nine digit floating point math package, full string features 
and data files. 

For computer aided instruction applications, a full feature 
version of PILOT is available. It includes math operators, 
misspelling match features and all other proposed for the 
ANSI! standard version. The 6800 multi-user system is just 
as economical, but far more flexible and powerful than 
multiple small machines for CAI applications. 

MUB-68 Multi-User Board and BASIC Software 

Assembled and tested $150.00 

Kit $129.95 




SOUTHWEST TECHNICAL PRODUCTS CORPORATION 

219 W. RHAPSODY 

SAN ANTONIO, TEXAS 78216 

Circle 350 on inquiry card. 



.4 




Model Z-2 

Up to 51ZK of RAM/ROM 



Fill your 



Model Z-2D 

One or two disks 

Up to 512K of RAM/ROM 

Up to 184K of disk 



kill 



System Two 

Dual disk 

Up to 512K of RAM/ROM 

Up to 184K of disk 



needs 



with the indiistryls 



mostprofessloiial 



:¥A 



ii ■ 



#1 IN RELIABILITY 

When you choose Cromemco you 
get not only the industry's finest 
microcomputers but also the indus- 
try's widest microcomputer selec- 
tion. 

What's more, you get a computer 
from the manufacturer that compu- 
ter dealers rate #1 in product re- 
liability.* 

Your range of choice includes 
our advanced System Three with 
up to four 8" disk drives. Or choose 
from the System Two and Z-2D with 
5" drives. Then for ROM-based work 
there's the Z2. Each of these com- 
puters further offers up to V2 mega- 
byte of RAM (or ROM). 

We say these are the industry's 
most professional microcomputers 
because they have outstanding fea- 
tures like these: 

• Z-80A microprocessor — oper- 
ates at 250 nanosecond cycle 
time — nearly twice the speed of 
most others. 



'Rated in The 1977 Computer Store 
Survey by Image Resources, Westlake 
Village, CA. 



Up to 512 kilobytes of RAM and 
1 megabyte of disk storage 




System Three 

Two to four disks 

Up to 51 2K of RAM/ ROM 

Up to 1 megabyte of disk 



21 card slots to allow for un- 
paralleled system expansion us- 
ing industry-standard S-100 
cards. 

S-100 bus — don't overlook how 
important this is. It has the in- 
dustry's widest support and Cro- 
memco has professionally imple- 
mented it in a fully-shielded 
design. 



Q 



• Cromemco card support of more 
than a dozen circuit cards for 
process control, business sys- 
tems, and data acquisition in- 
cluding cards for A-D and D-A 
conversion, for interfacing daisy- 
wheel or dot-matrix printers, even 
a card for programming PROIVIs. 

• The industry's most professional 
software support, including FOR- 
TRAN IV, 16K Disk-Extended 
BASIC, Z-80 Macro Assembler, 
Cromemco Multi-User Operating 
System — and more coming. 

• Rugged, professional all-metal 
construction for rack (or bench 
or floor cabinet) mounting. Cab- 
inets available. 

FOR TODAY AND TOMORROW 

Cromemco computers, will meet 
your needs now and in the future 
because of their unquestioned tech- 
nical leadership, professionalism 
and enormous expandability. 

See them today at your dealer. 

There's no substitute for getting 
the best. 



see next 



Circle 80 on inquiry card. 



Crontenteo 

Incorporated 
Specialists in computers and peripherals 
260 BERNARDO AVE., MOUNTAIN VIEW, CA 94040 • (415) 964-7400 







BYTE )ulv 1978 



SEE YOUR LOCAL DEALER 



Anchodie. AK 99501 
ALASKA DIVERSIFIED DIGITAL 
ITOOWniHiiKDAvtrnw 
(907) 2T7-63I2 

Hunlwllle. AL31WS 
COMPUTERLAND OF HUNTSVILLE 
3020 Unlvcrlily Drtvi. N.W. 
(20S) 539-1200 

*Llltle Rock, AR 72206 
COMPUTER PRODUCTS UNLIMITED 
2412Si>uihBr(Mdwiv 
{501) }T1 4)449 



Ph«ni>..AZ 85021 
COMPUTER RESEARCH CORP 
ZZ25 W Mm. View Ro^ - No, G 
(601)943-ST19 

PhMnU,AZB5029 
COMPUTER WORLD 
2230 Wnl LirkxHir 
[6021 943-S925 

laaan.Kiii'oraiSnt 
8VTE SHOP OF TUCSON 
26T2 E»t B'Bxfwiv 
(602) 327-4579 

• CuKin, CA 90746 
SUNSHINE COMPUTER COMPANY 
20710 Soulh Ltapwood AMOue 
(213)327.2118 



BYTE SHOP SACRAMENTO 
6041 Gi«enbick Low 
(91G|961.BYTE 

El Cerrllo, CA 94530 
COMPUTERLAND EL CERRITO 
1 1074 Sm Piblo Avenue 
(415)233-5010 

• FMinUin Valley, CA 92708 
ADVENTURES IN COMPUTING 
8TS6 WiriKi Avtniw 
(714) 848-83SS 

FrtMio, CA 93703 
BYTE SHOP OF FRESNO 
3139 t. McKinley Axniw 
(209)485-2417 

Hiy*iid, CA 94S42 
COMPUTERLAND OF HAYWARO 
22634 Foothill Boulevird 
(415) 138-8080 



ALGORITHM PERSONAL COMPUTERS 

7561 RhiTw Drive 

(714)751-8080 

lotfcwood, CA 90302 
COMPUTERLAND OF W. LOS ANGELES 
6840 Li CIciHii Boulcvird 
(213) 776-8080 

Lawndile. CA 93060 
BYTE SHOP OF LAWNDALE 
6S08 Hiwlhomc Boulrvud 
(2131371 2421 

•Lownti. CA 95650 
KINGMONT ENTERPRISES. INC. 
9900 KIni Roid 
(916)988-8189 

Los AnidM, CA 90025 

AMERICAN RECORDER COMPANY 

1655 Siwlclle Boulevard 

(213)477-2063 

McnIoPirk.CA 94025 

COMPUTADATA PROCESSING SERVICE 

2225 Shiion Roid - No. 224 

MlulonVlefo.CA 92630 
COMPUTERLAND SADDLEBACK VLV 
24001 Vij FjbrkBiM ~ No 904 
(714)7700131 



• Mounutn Virw. CA 94040 
BYTE OF Mt VIEW 
1063 W El Cjmino Reil 
(415)969-5464 

Oiutft. CA 92667 
COMPUTER MART 
633-a W«l KiltUt Bojlnard 
{714)633.1222 

Palo Alto, CA 94306 
BYTE SHOP PALO ALTO 
2227 El Camino Rnl 
(415) 327-8080 

Palo Alio. CA 94301 
MICROTECH EXPORTS 
912Cowp« SliHi 
(415)328-1712 

Paud>ni,CA9ll01 
BYTE SHOP PASADENA 
496 South Lake Avenue 
(213)684-3311 

Placcrville, CA 95667 
GRANITE BUSINESS SYSTEMS 
670 Plcaunl Valley Rud 
(916)626-1161 

Sacramento, CA 95816 
MICROCOMPUTER APPLICATIONS SYS 
2322 Capital AMniM 
(916) 433-4944 

San Diego. CA 92211 
COMPUTERLAND OF SAN DIEGO 
4233 Canroy Street 
(714) 560-9912 



THE CW4PUTER CENTER 
8205 Ronton Road 
(714) 192-5302 

San Fran(lico,CA 94105 
COMPUTERLAND OF SAN F RANCISCO 
117 Fremont Street 
(415) 546-1592 

• San FranclKO, CA 94103 
THE COMPUTER STORE OF S.F. 
1093 Motion Street 
(415)431-0640 

SanFraiH:iico.CA9411S 

THE NETWORK: 

495 Third Avenue -No. 8 

(415)221-1112 



•DENOTES SYSTEM THREE' DEALER 



San Joie.CA9SI14 

BYTE SHOP Mi ol SAN (OSt 

2626 Union Avenue 

(408) 377-4685 

San|ote.CA95123 
THE COMPUTER ROOM 

I24-HBIaiiamHi1l Road 
(408) 226-8383 

San(o»e,CA'9S132 
PLANE DATA WORKS 
3 584 Minio Court 
(408) 2624566 



(415)895-9363 

• San Mateo, CA 94401 
COMPUTER TERMINAL 
309 S. San Maleo Drive 
(415) 347-9894 

* Sania Ana, CA 92705 

ADVANCED MICROCOMPUTER PROD 

1310 £aii Edinger 

(714)558-881) 

Santa Oar a. CA 95051 

THE BYTE SHOP OF SANTA CLARA 

3400 El Cam.no Real 

(408) 249-4221 

THE COMPUTER STORE 

BZO Broadway 
(213)451-0713 

Sunnwak. CA 94086 
BYTE INDUSTRIES 
910 W Miudf 
(415)719-8000 



RECREATIONAL COMPUTER CENTER 
1324 South Mary Avenue 
(408) 712-)1IH 

Tinlin. CA 92680 
COMPUTERLAND OF TUSTIN 
104 Weil Flrtl Street 
(714) 544-0542 

•Van Nuyi.CA 91411 
COMPUTER COMPONENTS 
5848 Sepulveda Boulevard 



Walnut Creek. CA 94596 

BYTE SHOP COMPUTERS OF DIABLO VLY 

2989 N Main Street 

(415)933-6152 

EnflewDod, CO 80110 
BYTE SHOPOF ARAF _ _ 

3463 South Acoma Street 
(101) 76I4IZ1 

Fairfield, CT*06430 
COMPUTERLAND OF FAIRFIELD 
2475 Black Rock Turnpike 
(203) 374-2227 

WindMTLockt.CT 06096 
THE COMPUTER STORE 
61 South Main Street 
(203) 6174188 

Newark. DE 19711 

COMPUTERLAND OF NEWCASTLE CITY 

^ttro Shopping Cenler 

Kirkwood Highway 

(302) 738-9656 

Ft. Laudt.dak, FL J33J4 
BYTE OF FT LAUDERDALE 
1044 E Oakland Park Blvd. 
(105) 561 2983 

Ft. Lauderdale, FL 13312 
COMPUTERS FOR YOU, INC, 
3608 W Broward Blvd. 
(305) 581-8945 

• Ft Meyert.FL 33901 
MICROCOMPUTER SYSTEMS, INC 
12800 US 41 South 
(813)481-3376 

Planlallon.FL 33317 
COMPUTERAGE 
1400 SW. 70th Avenue 
(305) 791-8080 



(813) 879-4225 

• Atlanta, GA 30340 
ATLANTA COMPUTER MART 
S09t-B Buford Highway 



Marietta, GA 30060 
EDUCATIONAL DATA SERVICES 
79 On ford Road 

•Halku.Maui, HI 96708 
CAPACITY, INC 
P,0. Box A 
(808) 5752930 

•Honolulu. HI 96815 
COMPACT COMPUTERS 
305 Royal Hawaiian, Ste. 407 
18081 373 2751 

Kiilua, Oahu, HI 96734 
MICROCOMPUTER ENTERPRISES 
1450 Mokulua Drive 
(808) 261-3281 

Arlington Heigh ti, IL 60004 
COMPUTERLAND ARLINGTON HTS. 
50 Eati Rand Road 
(112)255-6488 

Champaign, I L 61820 
BYTE SHOP CHAMPAIGN 
1602 S Neil Street 
[217)352-2313 

Chicago. IL 60632 
BRONSON 1 BRATTON. INC. 
5161 S. Millard Avenue 
(312)735«20D 

Lide.lL 60532 

COMPUTER A CONTROL AFFILIATE 

4315 A>aiea.No.40l 

1312)9684548 

Lombard. IL 60148 

MIDWEST MICROCOMPUTERS, INC, 

708 South Main Street 

(312) 495-9889 

Napcrvillt, IL 60540 
ILLINI MICROCOMPUTERS 
61 2 Eati Olden Avenue 
(312)420UI3 

NHet. IL 60648 
COMPUTERLAND NILES 
9511 N. Milwaukee Avanut 
(311)967.1714 



BYTE luly 1978 



□ 



Oak Lawn. IL 60453 
COMPUTERLAND OF OAK LAWN 
10935 Soulh Citno Avenue 
(312)422-8080 

Ro<krDrd,IL 61101 

IMPERIAL COMPUTER SVSTEMS 

2105 -23rd Avenue 

(815) 22fr4200 



•Bloommgion, IN47401 
DATA DOMAIN 
406 South College Avenue 
(812)334-1607 

•Fort Wayne, IN 46805 
DATA DOMAIN OF FORT WAVNE 
2805 Eall Slate Boulevard 

(219)484-7611 

Indianapotli, IN 46268 

DATA DOMAIN OF INDIANAPOLIS 

7027 Michigan Road 

(317)251-3139 

West Lafayette. IN 47906 

DATA DOMAIN OF WEST LAFAYETTE 

219 Weu Columbia 

(317) 743-3951 

Mitiion, KS 66202 
COMPUTER CENTER 
5815 lohnsnn Drive 
(913)432-2983 

Overlaitd Park. KS 66106 

PERSONAL COMPUTER CENTER. INC. 

3819W 95lhSl>eet 

(911)649.5942 

Lexington, KV 40501 

DATA DOMAIN OF LEXINGTON 

506-1/2 Euclid Avenue 

(606) 233-3346 

Louifville, KY 40222 
COMPUTERLAND OF LOUISVILLE 
813-8 Lyndon Lane 
(502) 425-8308 

Louisville. KY 40220 

DATA DOMAIN OF LOUISVILLE 

3028 Hunlinger Lane 

(502) 456-5242 

Louisville, KV 40206 
PRAGMATECH 
2310 Hellwnod Avenue 
(S02) 89!-1230 

•Surtington, MA 01803 
THE COMPUTER STORE 

(617)272-8m 



College Park. MD 20740 
INTELLIGENT BUSINESS MACHINES 
7318 Baltimore. Avenue. Suite 100 
(301 ) 779-7998 

• P>kesville.MD21108 
MODULAR SYSTEMS, INC 
4005 Seven Mile Lane 
(301)4844322 

• Rockville, MD 20852 
COMPUTER WORKSHOP 
1776 east ttfferMn 
(301)468-0463 

Rockville, MD 20855 

COMPUTERLAND Of GAITHERSBURG 
16065 Frederick Road. Route 355 
(301) 948-7616 

Silver SpCing. MD 20901 
CAM ENGINEERING. INC 
9318 Worth Avenue 
(301) 589-1779 

•Tow«>n.MO*2I204 
COMPUTERS ETC. 

1 3-A Allegheny Avenue 
(301) 296-0520 

Ann ArtKH, Ml 48104 

NEWMAN COMPUTER EXCHANGE 

1250 North Main Sirect 

(113) 994-4445 

Ann Arboi, Ml 48104 
THE COMPUTER STORE 



Ann Arbor. Ml 48104 

UNITED MICROSYSTEMS CORP 

2601 South SUie Sireel 

(313) 6684806 

•Berrien Sprinp. Ml 49103 
THE ABACUS 

Route No 1, Box 191.(Nilet Avenue) 
(616) 429-3034 

Grand Rapidt. Ml 49508 
)EPSAN. GROUP K 
4706 Morningtlde Drive. S.E. 
(616)698-9057 

Royal Oak, Ml 48073 

COMPUTER MART OF ROYAL OAK 

1800 Weil 14 Mile Road 

(313)576-0900 

Edina, MN 55435 
COMPUTER DEPOT, INC 
3511 Wnf 70th Street 
(612) 927-5601 

Chettertield. MO 63017 

COMPUTER SYSTEMS CTR ST. LOUIS 

13461 Olive Boulevard 

(314) 576-5020 



COMPUTERLAND OF NASHUA 
419 Amhertt 
(603) 889-5238 

Hoboken. N) 07030 
HOBOKEN COMPUTER WORKS 
No, 20 Hudson Place 
(201)420-1644 

•itelln.NI 08830 
COMPUTER MART OF NEW JERSEY 
501 Rout* No 27 
(201) 2834)600 

Morriiio<vn,N) 07960 
COMPUTERLAND OF MORRISroWN 

(301) 53*4077 



Reno, NV 89502 
BYTE SHOP OF RENO 
4104 Kieuke Lai» 
(101) 826-8080 



• Buffalo, NY 14226 
CORSON COMPUTER CORP.. INC. 
3834 Main Street 
(716) 832-0662 

OeWilt,NY13214 
COMPUTER ENTERPRISES 
3470 Erie Boulevard Eati 
(315)446-1284 



LOUIS SCHAEfFER 

119 Hamlllon Avenue 
(516)374-1286 

•Hollit,NY 11423 
SYNCHRaSOUND ENTERPRISES 
193-25 limaica Avenue 

[112)468-7067 

Ithaca, NY 14850 
COMPUTERLAND OF ITHACA 
235 Elmira Road 
(607) 277.4888 

New York City. NY 10016 
BYTE SHOP EAST 
130 E. 40th Street 
[31 2) 889-4204 

Rocheiler.NV 14609 
COMPUTER HOUSE, INC 
731 Atlantic Avenue 
(716)654-9218 

• Cincinnatt. OH 45409 
DIGITAL DESIGN 

7694 Camargo Rd. [Madiera) 
(513)5614733 

Cincinnati. OH 45202 
21ST CENTURY SHOP 
16 Convention Way 
Skywalk, Vine A Race 
(513)651-2111 

Columbui, OH 43201 

MIDWESTERN DIGITAL ELECTRONICS 

80 Weil Line Avenue, Suite 1J 

(614) 294-2991 

•Oaylon, OH 45409 
DATA DOMAIN Of DAYTON 
1932 Brown Street 
(513) 223-2348 

Keni. OH 44240 
OHIO MICRO SYSTEMS 
233 South Water Street 
(216) 678-5202 

Mayfietd Heights, OH 44124 
COMPUTERLAND OF CLEVELAND EAST 
1288 Sam Center Road 
(216) 461. 1200 

Oklahoma City, OK 73106 
HIGH TECHNOLOGY 
1611 Norlhwett 23rd Street 
(405) 528-8008 

Beaverion OR 97005 
BYTE SHOP OF BEAVERTON 
3482 S W Cedar HUh Boulevard 
(503) 644-1687 

Eugene, OR 97401 
REAL OREGON COMPUTER CO- 
205 Wett Tenth Street, P O. Boi 12 
(503) 4841 040 

• Tualatin, OR 91062 
CREATIVE SYSTEMS 
8101 S W. Nyberg Road 
(503) 638-8406 

Alliun Park, PA 15101 
R. OONKRIGGER 
93BO SpringTIel 
(412) 3f 



Huntington Valley. PA 19006 
MARKETLINE SVSTEMS, INC 
2337Phllmoni Avenue 
(315)9474670 

King of Pruttia, PA 19406 
COMPUTER MART OF PENNSYLVANIA 
550 Oe Kalb Pike (Route 302) 
(215) 26S-2580 

Piinburgh, PA 15237 
ELECTRONICS PLACE 
7250 McNlght Road 



Warwick, Rl 02886 
COMPUTER POWER, INC 
1800 Pott Road 
(401) 738-4477 

• Columbia. SC 29205 
BYTE SHOP OF COLUMBIA 
1018 Green Street 

(803) 771-7814 

Mcmphit.TN 38101 
COMPUTER STORE 
1162 Couitland Place 
(901)274-1938 

Nashville, TN 37206 
COMPUTER WORLD 
625 Main Street 
(611)2444094 

• Nashville. TN 37211 
SURYA CORPORATION 
5755 Nolentville Road 
(615)834-1638 

Amarlilo, TX 79109 
COMPUTER CORNER, INC. 
1800 Soulh Georgia St., No. 3 
(806)313-4194 

• Austin, TX 78731 
COMPUTERS N THINGS 
2835 Hancock Drive 
(512)451-5970 



MICRO SVSTEMS SERVICES. INC 
5301 Everhari, Space H-PO. Boi6131 
(512)8554516 

• DallB.TX 71243 
COMPUSHOP 

211 Keyston Park. 13933 North Central 
(214) 234-3412 

•Houiton.TX 77057 
COMPUTERLAND OF S.W HOUSTON 
6439 Westheimer 
(713)977-0909 

•Houston, TX 77006 
COMPUTERTEX 
2100 Richmond Avenue 
(711) 5264934 

Hounon.TX 77036 
INTERACTIVE COMPUTERS 
7646-1/2 Dathwood. P.O. Box 36584 
(713)977-7037 



Crametneo 

incorporated 
Specialists in computers and peripherals 
280 BERNARDO AVE., MOUNTAIN VIEW, CA • (415) 964-7400 



•Houtton.TX 77098 
THE MOS 

1853 Richmond Avenue 
(713) 527-8008 

Lubbock, TX 79412 
COMPUTER MART OF W TEXAS 
3506 Avenue, O 
(806)765-7134 

Richardson. TX 75080 

THE MICRO STORE 

634 South Central EiprcHway 



Provo, UT 84601 

THE COMPUTER WORKS 

735 South State Street, P.O Box N 

(801) 373-7522 

AInandria, VA 22304 
COMPUTERS PLUS, INC 
678 S Pkkeli Sireel 
{703)751-4656 

McLean, VA 22101 
COMPUTER SVSTEMS STORE 
1984 Chain Bridge Road 
(703)831-8333 

Seattle, WA 981 15 

THE RETAIL COMPUTER STORE 

410 N,E 71nd Street 

(206) 524-4101 

•AppleltMi,WI 54911 
SOUND WORLD, INC. 
3015 W Wiscomin Avenue 
(414) 7)4-7698 

Maditon, Wl 53711 

THE MADISON COMPUTER STORE 

1861 Monroe Street 

(608) 255-1153 

Milwaukee. Wl 51208 
MILWAUKEE COMPUTER STORE 
4710 Wett North Avenue 
(414) 445-4280 



•Racine. Wl S1405 
COLORTRON TV 
2111 UthrnpAvenu 
(414)617-2003 



• INTERNATIONAL • 



SONTROM INSTRUMENTS 



Croydon. Vkt-.Ausirilia, 3136 
COMPUTER ART A EDUCATION 
1 Stephen Cretcent 



Prahran. Vic I aria, Australia. 3181 
GEMINI MICROCOMPUTERS 
P.O. Box 99 

Wett Penh, 6001. W Autt Ta 
AUSTRALIAN COMPUTER PRODUCTS 
1 300 Hay Street 
(091.3224497 

• A-3401 Fishamend, Austria 
KREBSGES. MBH, 
Hainburgcr Stiabe 34 
013326818223 

Calgary, Alberta, Canada 
ROBO-TRONICS 
509-16 Avenue N,W. 
(403) 282-9496 

Montreal, Quebec. Can H3B 3C9 
FUTUR BYTE, INC- 
1191 Phillips Square 
(114)861-3120 

Toronto, Ont. Can. M4G 3B5 
COMPUTER MART, LTD 

1143 Bayvlew Avenue 
(416)484-9708 

Toronto, Ont , Can. M4R 1A1 

FIRST CANADIAN COMPUTER STORE 

44 Eglinton Avenue We« 

(416)482-8080 



TRINTRONICS, LTD. 
186 Queen Street West 
(416) 598-0260 



ingdon. 
IWNJ 



Cambi., England PE1 
COMART LIMITED 
24 A Market Square 
0480-215-005 

Parii 15011, France 
COMPUTER BOUTIQUE 
149 Avenue dcWapam 

Chtyoda-Ky, Tokyo 101, )a 
BYTE SHOP S(XK)H 
1 44 Sotokanda 
03 251-1984 



Tokyo 106, Japan 

lEE CORPORATION 

4-33, 3-Chome, Ropongi. Minitoka 

(03)585-2331 

•MexicolS, DF. MexKO 
INTELEX.SA 
PA. De Lot Santos 70 
(905)516-9970 

Makati, Riial, The Phiillplnei 
DECISION SYSTEMS CORP. 
150 Amanolo St, A Pisay Rd. 
Lcgatpi Village 

• 10052 Stockholm 29, Sweden 
DATORISERING KONSULT AB 

F*ck3 

4051 batel. SwiiierUnd 
EUREX.INC 
Beinwiier Sir. 11 
061-157069 

• SOOlZurich.'swiiierluHl 
COMICRO AC 
Badeneniratte 281 

•Hiltrup4400,Muniler,W Germany 
BASIS MICROCOMPUTER VERTRIEB 
Von-Flotow-Sfabe I 
02501-4800 

•2000Wedel.H«leln.W Germany 
DIGITRON IC tOMPUTERSVSTEME 
Elei Der Doapdkche 3-1 
04103 7393 



-i i 



u 



•s 



Circle 80 on Inquiry card. 



^ 

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12 
28 
60 
72 
98 
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162 

32 

42 
48 
64 
84 
124 



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112 

115 

117 
118 
118 
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177 
206 
208 
208 



In the Queue 



Foreground 



KIMER: A KIM-1 TIMER 

Software— Baker 
THE AXIOM EX800 PRINTER: A User's Report 

Product Description— Bosen 
THE Z-80 IN PARALLEL 

Hardware— Loewer 
CONTROLLING DC MOTORS 

/hardware— Walton 
BUILD A KEYBOARD FUNCTION DECODER 

Hardware— Ciarcia 
A HIGH LEVEL LANGUAGE FOR 8 BIT MACHINES 

Software— Williams-Conley 
HOW TO GET YOUR TARBELL GOING 

Hardware— Weinstein 



Background 



TOP-DOWN MODULAR PROGRAMMING 

Software— Hearn 
WHO'S AFRAID OF DYNAMIC MEMORIES? 

Memory Design Tutorial— Haucl< 
ANTIQUE MECHANICAL COMPUTERS, Part 1 : Early Automata 

His tory— Williams 
THE FIRST TEN YEARS OF AMATEUR COMPUTING 

History— Libes 
A SHORT HISTORY OF COMPUTING 

History— Reid-Green 
HOW TO CHOOSE A MICROPROCESSOR 

Architecture-Frenzel 



Nucleus 



In This BYTE 

Some Thoughts About Modems 

Letters 

The Second West Coast Computer Faire 

Clubs, Newsletters 

Languages Forum: BASIC to Assembly Language Linkage 

Technical Forum: Fooling with the Stack Pointer 

More on Varistors 
Book Reviews 
BYTE's Bits 
BYTE's Bugs 

Programming Quickies: Beating North Star-MITS Incompatibility 
College Sports Report 
Event Queue 
What's New? 
Unclassified Ads 
BOMB 
Reader Service 



EiiTE 



July 1978 




BYTE is published monthly bv BYTE Publications Inc. 70 Main St, Peterborough NH 03458. Address all mail except sub- 
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postage paid at Peterborough NH 03458 and at additional mailing offices-USPS Publication No. 102410. Canadian second 
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possessions. In Canada and Mexico, $17.50 for one year, $32 for two years, and $46.50 for three years. $25 for a one year 
subscription by surface mail worldwide. Air delivery to selected areas at additional rates available upon request. $25 for a one 
year subscription by air delivery to Europe. Single copy price is $2.00 in the USA and its possessions, $2.40 in Canada and 
Mexico $3 50 in Europe, and $4.00 elsew/here. Foreign subscriptions and sales should be remitted in United States funds. 
Printed' in United States of America. Each separate contribution to this issue and the issue as a collective work copyright la 
1978 by BYTE Publication Inc. All rights reserved 

Subscription WATS Line: (800) 258-5485 



Volume 3 Number 7 



PUBLISHER 

Virginia Londner 

EDITOR IN CHIEF 

Car! T Helmers |r 

VICE-PRESIDENT, PRODUCTION 

Judith Hjvey 

PRODUCTION MANAt.ER 

Karen Gregory 

ADVERTISING DIRECTOR 

EAST, MIDWEST 

John Hayes 

ADVERTISING DIRECTOR 

WEST, SOUTHWEST 

Debra Boudrreau 

CIRCULATION MANAGER 

Gregorv Spiufaden 

SENIOR EDITOR 

Christopher P Morgan 

BOOK EDITOR 

Blaise W Lifflck 

COMPTROLLER 

Michael Galan 

EDITOR 

Raymond A G Cole 

PRODUCTION EDITORS 

David William Hayward 

Nancy Salmon 

BOOK PUBLISHER 

Thomas ) Herman 

BOOK PRODUCTION 

Edmond C Kelly |r 

NEW PRODUCTS EDITOR 

CLUBS, NEWSLETTERS 

Laura A Hanson 

ASSISTANT TO COMPTROLLER 

Rulh M Walsh 

EDITORIAL ASSISTANT 

Becky LifTick 

ADVERTISING 

Noreen Bardstey 

JillCallihan 

Patricia Clark 

PRODUCTION ASSISTANT 

Cheryl A Nurd 

CIRCULATION ASSISTANTS 

Sarah Bauhan 

Christine Dixon 

Ann Graves 

Pamela R Heaslip 

DEALER SALES 

Ginnie F Boudrieau 

TRAFFIC MANAGER 

Thomas Harvey 

ART 

Stephen Kruse 

Wai Chiu Li 

Dorothy Shamonsky 

Ellen Shamonsky 

RECEPTIONIST 

Jacqueline Earnshaw 

DRAFTING 

Techart Associates 

TYPOGRAPHY 

Goodway Graphics 

PHOTOGRAPHY 

Ed Crabtrce 

PRINTING 

The George Banta Company 

ASSOCIATE EDITOR 

Daniel Fylstra 

ASSOCIATES 

Walter Banks 

Steve Ciarcia 

David Fytsira 

Portia Isaacson 



ADVERTISING SALES REPRESENTATIVES 

EAST, MIDWEST 

Hajar Associates Inc 

17 DuranI S( 

WeslRoxbury MA 02132 

(617)325 5380 

100 W Chicago Av 

Chicago IL 60610 

(312)3378008 



WEST, SOUTHWEST 
Buckley /Boris Associates Inc 
91 2 South Barrington. Suite 202 
Los Angeles CA 90049 
(213)826-4621 

DISTRIBUTORS 
EASTERN CANADA 
RS-232 Distribution Company 
186 Queen St W. Suite 232 
Toronto ONTARIO 
WESTERN CANADA 
Kitronic Ltd 
26236 26th AvRR 5 
Aldergrove BC VOX 1A0 



July 1978 ©BYTE Publications Inc 



This month's cover shows Bab- 
bage's 1822 difference engine, a device 
designed to calculate values in mathe- 
matical tables. Charles Babbage was 
one of the earlier pioneers in the field 
of computational machinery, whose 
work paved the way for later break- 
throughs in computing. 



In This El^YE 



One way to demonstrate your 
KIM-1 computer is to use it as a clock. 
Robert Baker's article KIMER: A 
KIM-I Timer shows you how to 
display hours, minutes and seconds 
on the computer's LED display. The 
program can also be used as a timer. 

page 12 

Heat sensitive aluminized paper is 
the key ingredient in Axiom's unusual 
EX800 printer. Find out about one 
user's reactions to this peripheral in 
The Axiom EX800 Printer: A User's 
Report by R J Bosen. page 28 

Transforming the goal "I want thus 
and so function" into a program which 
performs that function is an act of 
design. Albert D Hearn provides the 
novice programmer with some back- 
ground philosophy about design of 
personalized programs in his article 
entitled Modular Programming. 

page 32 

Are you afraid of dynamic mem- 
ories? Let author Lane T Hauck 
remove some of the mysteries about 
these devices in Who's Afraid Of 
Dynamic Memories? The greatest 
potential of the dynamic memory for 
the experimenter is its low price; 
reading the article should prove to be a 
"refreshing" experience. page 42 

Dr James M Williams takes readers 
on a fascinating tour of early experi- 
ments in automata in his article 
Antique Mechanical Computers, Part 
1: Early Automata. Read about Vau- 
canson's mechanical duck and the 

4 July 1978 ® BYTE PuWicatioiB Inc 



Other miraculous pre-19th century 
devices that foreshadowed today's 
computers. page 48 

Today more and more design 
engineers are introducing parallel 
processing into computer systems to 
improve throughput rates. With the 
advent of inexpensive microprocessors, 
experimenters can now investigate this 
fascinating area. Find out more by 
reading Robert Loewer's The Z-80 
in Parallel. page 60 

When did personal computing really 
begin? Was it 1974 or 1971? The sur- 
prising answer is 1966. Sol Libes' The 
First Ten Years of Amateur Comput- 
ing traces the growth of this rapidly 
growing field over the past decade, 
and gives credit to the true pioneers. 

page 64 

The ability to control DC motors 
allows you to imagine applications 
from games to robotics. Robert L 
Walton describes a simple method of 
shaft position control in his article, 
Controlling DC Motors. page 72 




Have you ever wondered how this 
business of computing ever got 
started? And just what were the major 
developments and discoveries that 
made the computer industry what it is 
today? Well, take A Short History of 
Computing course by reading the 
article by Keith S Reid-Green. It 
provides a perspective on the antece- 
dents of today's developments in the 
field of computing. page 84 



If you would like to turn your 
printer or other peripheral on and off 
from your computer keyboard, Steve 
Ciarcia describes a simple way to do 
it with an EROM in Ciarcia's Circuit 
Cellar: Build a Keyboard Function 
Decoder. page 98 

How do I choose a microprocessor 
for personal computing? In some 
respects the problem is analogous to 
attempting to choose between a V-8 
and a V-6 automobile engine of the 
same horsepower: both make the 
car go and most users couldn't care 
less about the type of engine so long 
as the car gets them to their desired 
destinations. Similar considerations 
apply in the choice of a personal 
computer product based on the 
microprocessor it contains. Who 
cares what microprocessor the prod- 
uct contains, so long as it accom- 
plishes a certain minimum level of 
function with respect to systems 
and applications software? Lou 
Frenzel of the Heath Company gives 
some thoughts on How to Choose a 
Microprocessor in an article in this 
issue. page 124 

Thinking of writing your own high 
level language interpreter for your 
home computer? If so, Ted Williams' 
and Steve Conley's article, A High 
Level Language for 8 Bit Machines, 
will supply you with an overview of 
one such implementation. The lan- 
guage that they develop is suitable for 
use as both an interpreter or a 
compiler. page 152 

If you own a Tarbell cassette inter- 
face, read How to Get Your Tarbell 
Going. Author Larry Weinstein ex- 
plains how the unit works and gives 
some suggestions for improving 
performance. page 162 




A- 

I- 



: i 



' A 






The Ultimate Turn-on 




On/off control every viiere- 
by computer over the AC wiring 



Now it's simple and economical 
to control AC devices remotely from 
an S-100 or Apple II computer. 
Mountain Hardware's new Introl™ 
system delivers on/off commands 
over the existing AC lines — so you 
don't have to string a foot of ware! 

Control at any AC outlet. The 

Introl system impresses a code- 
modulated 50 KHz control signal 
on the house wiring. Then decodes 
the signal at any outlet to switch 
AC devices on and off. You can 
control lights, refrigerators, TVs, 
solenoid valves, sprinklers, burglar 
alarms — and many other things we 
leave to your fertile imagination. 
With the addition of input sensors 
to your computer system, you can 
automatically control variables such 
as temperature and soil moisture. 

Here's how it works. You plug 
m a single AC Controller board at 
the computer bus and connect the 
AC Interface Adapter to any con- 
venient 115 VAC outlet. The AC 
Controller is now connected to 
address as many as 64 channels 
remotely. But it's completely isolated 



from the 1 15v power, so there's no 
chance of short or shock. 

At any outlet where you seek 
control, plug in a Dual Channel AC 
Remote. Then plug one or two 
devices to be controlled into the 
box. Every AC remote has two 
independent 500 watt channels. 
When commanded by the computer, 
the Dual Channel AC Remote turns 
the devices on and off independ- 
ently. When polled by the compu- 
ter, the Dual Channel AC Remote 
sends a signal back, telling the 
computer the status of each device. 
Bidirectional communication pro- 
vides error free operation. 

Simple programming. You write 
your control program in BASIC or 
Assembler language. Software sub- 
routines for the control programs 
come with the eguipment — along 
with complete documentation. With 
your computer, you can program 
on/off commands at any day and 
time using our optional Clock 
boards for S- 100 or Apple II com- 
puters. A self contained power 
source assures fail safe operation. 



Modest prices. The Introl 
Remote Control System consists of 
one AC Controller, either S-100 or 
Apple II, and one Dual Channel AC 
Remote. It costs $329 completely 
assembled and tested. Additional 
Dual Channel AC Remotes are $99. 

The 100,000 Day Clock for 
S-lOO's costs $219 assembled and 
tested. The Apple Clock costs $179 
assembled and tested. 

All prices are f.o.b. Scotts Valley, 
CA. Prices are USA Domestic. Cal- 
ifornia residents add 6% sales tax. 

Where to find it. The Introl 
System can now be found at compu- 
ter shops throughout the U.S. and 
Canada. Drop by and ask for a dem- 
onstration. Mountain Hardware, 
Inc., 5523 Scotts Valley Dr., Scotts 
Valley, CA 95066. (408)438-4734. 



AC Controller (Apple) 




Dual Channel AC Remote 



OS 



Circle 260 on inquiry card. 



^ Mountain Hardware 



AC Controller (S-100) 

BYTE July 1978 5 



a 



EdilopisI 






Some Thoughts About Modems 



By Carl Helmers 



Articles Policy 

By J t Publkatiom Im is coniinuully 
seeking quality manuscripts written by 
individuals who are applying personal 
computer systems, designing such sys 
terns, or who have knowledge which 
will prove useful to our readers, hor 
a more informal description ot pro- 
cedures and requirements, potential 
authors should send a self-addressed, 
stamped envelope to BY ft Authors 
Guide, 70 Main St, Peterborough NH 
034 iS. 

Articles which are accepted are 
purchased with a rate of $4 5 per pub- 
lished page, based on technical quality 
and suitability lor the intended reader 
ship. As to articles appearing in BY It 
magazine, each month, the authors of 
the two leading articles in the reader 
poll (BYTt's Ongoing Monitor Box or 
"BOMB") are presented with bonus 
checks of fWO and 150. Unsolicited 
materials should be accompanied by 
lull name and address, as well as return 
postage.^ 



In the June 1978 issue of BYTE, on pages 
103 and 104, we printed a short report on 
activities of Ward Christensen and Randy 
Suess of the Chicago Area Computer Hobby- 
ist Exchange (or CACHE). These two gentle- 
men have implemented a sort of public 
bulletin board in the form of a computer 
system which answers the phone through an 
auto answer modem, determines the data 
rate of the caller's modem, generates an 
interactive self-documenting conversation, 
and is able to store messages on a floppy 
disk. (For those who missed the original 
notice, the phone number to call is (312) 
528-7141. You will need a Bell 103 style 
modem running in originate mode at 110 or 
300 bps. I 

Another very active input is the continu- 
ing activity of the PCNET committee on the 
West Coast, which will sooner or later get 
around to defining a protocol appropriate to 
a number of users talking to each other. I 
also received considerable inspiration from a 
memo on Telemail put out by Ken Bowles 
of the University of California at San Diego. 
All these inputs add up to this present ex- 
ploration of the state of modem technology 
as applied to the personal computer. 

If you look into the technology of tele- 
communications, it is easy to get turned off 
by timesharing. After all, what reason is 
there to have your own computer if it is not 
to avoid all that accounting and bill paying 
on an hourly basis which is use of a time- 
sharing account? Isn't it better to pay a 
lump sum and have a self-contained com- 
puter which runs without any outside ties? 
This view of identity between timesharing to 
a big computer and telecommunications in 
general has been a somewhat erroneous con- 
clusion in my world view for several years. 

The conclusion is easy to arrive at, since 
virtually all use of moderately large com- 
puters is done by timesharing telecommuni- 
cations facilities. But viewpoints change 



when an open mind is maintained. The 
demonstration provided by the gentlemen of 
CACHE is a key input which sent me on an 
intellectual excursion into simple, easily im- 
plementable uses of the small computer with 
the phone network. The ideas which come 
from these thoughts are oriented towards a 
small integer number of people communi- 
cating with one another. These ideas are the 
kind which can be implemented whenever 
two or a few people share a common goal 
and live far enough away from one another 
to make telecommunications via their per- 
sonal computers a useful practice in lieu of 
physical travel. The technology is present 
and fairly inexpensive, so there is no reason 
why it should not be used. And, as readers 
will find in the form of future articles in the 
magazine, the technology is being used. Now 
let's turn to two characteristic models of 
modems and what they can do for their 
owners. 

Simple Communications: 

Two Computers + Two People + One 
Phone Line + Acoustic Couplers 

One of the simplest of models to imple- 
ment in this sphere of computer to com- 
puter data communications is duplex trans- 
mission through the phone with similar 
modems at each end. For example, let us 
suppose that two readers are each the owner 
of a personal system with a spare serial port 
talking RS-232 levels to an acoustic modem. 
Further, let's suppose that they want to talk 
to one another using digital techniques to 
send words by way of the phone line. An 
ordinary telephone of the household variety 
is their link to each other via the phone net- 
work. A simple program model for conversa- 
tions carried out through a typewriter style 
terminal keyboard with a display of mes- 

Continued on page 104 






:» 



! 



luly 1978®BYTE Pgblicilions Inc 



7 



THE COMPLETE (DO 



1 








LookToThe North Star HORia)N Computer. 



HORIZON™— a complete, high-performance microprocessor 
system with integrated floppy disk memory. HORIZON is 
attractive, professionally engineered, and ideal for business, 
educational and personal applications. 

To begin programming in extended BASIC, merely add a CRT 
or hard-copy terminal HORIZON-1 includes a Z80A processor, 
IbK RAM, minifloppy™ disk and 12-slot S-100 motherboard 
with serial terminal interface — all standard equipment. 

WHAT ABOUT PERFORMANCE? 

I he ZbOA proc essor operates at 4MHZ — double the power of 
the 8080 And our 16K RAM board lets the Z80A execute at 
full speed. HORIZON can load or save a 10K byte disk program 
in less than 2 seconds. Each diskette can store 90K bytes. 

AND SOFTWARE, TOO 

HORIZON includes the North Star Disk Operating System and 
full extended BASIC on diskette ready at power-on. Our BASIC, 
now in widespread use, has everything desired in a BASIC, in- 
cluding sequential and random disk files, formatted output, a 
powerful line editor strings, machine language CALL and more. 



EXPAND YOUR HORIZON 

Also available - Hardware floating point board (FPB); addi- 
tional 16K memory boards with parity option. Add a second 
disk drive and you have HORIZON-2 Economical serial and 
parallel I/O ports may be installed on the motherboard. Many 
widely available S-100 bus peripheral boards can be added to 
HORIZON 

QUALITY AT THE RIGHT PRICE 

HORIZON processor board, RAM, FPB and MICRO DISK SYS- 
TEM can be bought separately for either Z80 or 8080 S-100 bus 
systems. 

HORIZON-1 $1599 kit; $1899 assembled. 

HORlZON-2 $1999 kit; $2349 assembled. 

16K RAM-$399 kit; $459 assembled; Parity option $39 kit; $59 
assembled. FPB $259 kit; $359 assembled. Z80 board $199 kit; 
$259 assembled Prices subject to change. HORIZON offered 
in choice of wood or blue metal cover at no extra charge 

Write for free color catalogue or visit your local computer store. 



North Star * Comruters 

2547 Ninth Street • Berkeley, California 94710 • (415) 549-0858 



Circle 285 on inquiry card. 



BYTt July 1978 



Sol Terminal Computer 




The answer is d 



It^ the serious 
solution to the 
small computer 
question. 

Sol Systems are the key to effective, economical 
small computer power. Sol Systems give you the force of a 
powerful general purpose computer, the problem solving 
capability of high level languages and the operational simplicity 
of everyday office equipment. 

From the ground up, Sol Systems were designed to do 
a complete job without adding a load of costly extras. In fact, 
when you compare the "everything included" price of 
a quality, field proven Sol System with anything else on the 
market, you'll be happily surprised to find out how little 
the extra performance and convenience costs. 



For example, complete Sol Systems with 16,384 bytes 
of RAM memory start at less than $2500? Expanded systems • 
with 49,152 bytes of RAM memory, 1.5 million bytes of 
on-line disk memory, disk operating system and Extended 
Disk BASIC cost less than $8000? Both systems are fully n 

assembled, burned-in, tested and ready to go. 

Sol Compatibility 

Sol Systems feature the S-100 bus for pin-to-pin ■• 

compatibility with a wide variety of add-on devices such as 
voice input and computer graphics. Standard Sol 
parallel and serial interfaces will drive most standard printers, - 
modems and other peripherals. 

A word about languages 

No system is complete without software, and at Processor 
Technology we have tailored a group of high level languages, 
an assembler and other packages to suit the wide capabilities 
of our hardware. * 

Take a look at our exclusive Extended BASIC as an example. 
In cassette form, this BASIC features string and advanced 

*U.S. prices only. 






Sol System. 



file handling, special screen commands, timed input, complete 
matrix, logarithmic and trigonometric functions, exponen- 
tial numbers, 8 digit precision and square root. The language 
handles serial access files, provides tape rewind and 
offers cursor control for graphics capability. 

The disk version has all the number crunching talents 
of the cassette BASIC plus instant access to data and programs 
on floppy disks. It includes random as well as sequential 
files and a unique ability to update sequential data in place. 

Processor Technology FORTRAN is similar to FORTRAN IV 
and has a full set of extensions designed for the "stand alone" 
computer environment. Thousands of special application 
programs available through books and periodicals have already 
been written in this well established language. 

Processor Technology PILOT is an excellent language 
for teachers. It is a string-oriented language designed expressly 
for interactive applications such as programmed instruction, 
drill and testing. 

No wonder we call it the serious solution 
to the small computer question. 

It's the small computer system to do the general ledger and 



the payroll. Solve engineering and scientific problems. 
Use it for word processing. Program it for computer aided 
instruction. Use it anywhere you want versatile 
computer power! 

Sold and serviced only by the best dealers. 

Sol Systems are sold and serviced by an outstanding group 
of conveniently located computer stores throughout the 
United States and Canada. They are also available in Australia, 
Europe, the United Kingdom, Central America, South 
America, Japan and Singapore. 

For more information contact your nearest dealer listed on 
the following page. Or write Department B, Processor 
Technology Corporation, 7100 .Johnson Industrial Drive, 
Pleasanton, CA 94566. Phone (415) 829-2600. 

Circle 305 on inquiry card. 



Processorlechnology 



See Sol at all these fine 
computer centers. 



ALABAMA 

Birmingham ICP— Computerland 

(205) 979-0707 

CALIFORNIA 

Costa Mesa Orange County 

Computer Center (714)646-0221 

Hayward The Byte Shop 

(415) 537-2983 

Hayward Computerland of 

Hayward (415)538-8080 

Lawndale The Byte Shop 

(213)371-2421 

Modesto Computer Magic 

(209) 527-5156 

Mountain View Digital Deli 

(415) 961-2670 

San Rafael The Byte Shop 

(415)457-9311 

Tarzana Byte Shop of Tarzana 

(213) 343-3919 

Walnut Creek The Byte Shop 

(415)933-6252 

COLORADO 

Boulder The Byte Shop 

(303) 444-6550 

Denver The Byte Shop 

(303) 399-8995 

FLORIDA 

Ft Lauderdale . Byte Shop of 

Ft, Lauderdale (305) 561-2983 

Miami Byte Shop of Miami 

(305) 264-2983 

Tampa 



Microcomputer 

Systems Inc. (813) 879-4301 

Atlanta Computer Mart 
(404) 455-0647 

The Data Domain 
(312)397-8700 

IOWA 

Davenport , The Computer Store 

of Davenport (319) 386-3330 



GEORGIA 

Atlanta 

ILLINOIS 

Schaumburg 



MARYLAND 

Towson Computers, Etc. 

(301)296-0520 

MICHIGAN 

Ann Arbor The Computer Store of 

Ann Arbor (313) 995-7616 

MINNESOTA 

Minneapolis Computer Depot 

(612)927-5601 

NEVADA 

Reno Byte Shop of Reno 

(702) 826-8080 

NEW JERSEY 

Cherry Hill Computer Emporium 

(609) 667-7555 

Iselin The Computer Mart of 

New Jersey (201)283-0600 

NEW YORK 

Endwell 

New York 
White Plains 



The Computer Tree 

(607)748-1223 

... The Computer Mart of 
New York (212)686-7923 



The Computer 
Corner (914)949-3282 

NORTH CAROLINA 

Raleigh ROMs N RAMs 

(919) 781-0003 

OHIO 

Akron Basic Computer Shop 

(216) 867-0808 

Columbus The Byte Shop 

(614) 486-7761 



Dayton 

OREGON 

Beaverton 

Eugene 
Portland 



Computer Mart of 

Dayton (513)296-1248 

Byte Shop Computer 

Store (503)644-2486 

The Real Oregon 

Computer Co (503) 484-1040 

. . Byte Shop Computer 
Store (503)223-3496 



RHODE ISLAND 

Warwick 

SOUTH CAROLINA 

Columbia 



Computer Power. Inc. 
(401) /38-4477 



The Byte Shop 
(803) 771-7824 



TENNESSEE 

Kingsport Microproducts & 

Systems (615) 245-8081 

TEXAS 

Arlington Computer Port 

(817)469-1502 

Houston Interactive Computers 

(713) 772-5257 

Lubbock Neighborhood Computer 

Store (806)797-1468 

VIRGINIA 

McLean The Computer Systems 

Store (703)821-8333 

WASHINGTON 

Bellevue Byte Shop Computer 

Store (206) 746-0651 

WISCONSIN 

Madison The Madison Computer 

Store (608)255-5552 

Milwaukee The Milwaukee 

Computer Store (414) 259-9140 

WASHINGTON, D.C. 

Washington, DC Georgetown 

Computer Store (202)362-2127 

CANADA 

London, Ontario The Computer 

Circuit Ltd (519) 672-9370 

Toronto, Ontario Computer 

Mart Ltd. (416) 484-9708 

Vancouver B.C Basic Computer 

Group Ltd (604)736-7474 

Vancouver, B C Pacific Computer 

Store (604)438-3282 

AUSTRALIA 

Victoria Sontron Instruments 

(03) 569 7867 

PHILIPPINES 

San Juan, Metro Manila Integrated 

Computer Systems, Inc. 

JAPAN 

Tokyo Moon base Shinjuku 

(03) 375-5078 5079 



H 






m. 



■*? 



*IE 



ProcessorTechn< 



10 BY Tt |ul> 1978 



§ §!• 



ly 



Circle 305 on inquiry card. 



Letters 



DESIGNERS BEWARE: SOME 2716 
CONFUSION 

I just came across a very untidy situ- 
ation involving read only memory num- 
bers which may be of interest to a great 
number of readers. We are all familiar by 
now with the advantages of the 2716 
erasable read only memory; however, 
everyone should be aware that while the 
Intel version (and possibly others) re- 
quires only a single +5 V supply, Texas 
Instruments makes a similar device with 
identical memory organization, number 
TMS2716 that requires ±5 V and +12 V 
supplies. This part is designed to be pin 
compatible with the older 2708s. Texas 
Instruments has another part labeled 
TMS2516 which is pin compatible with 
an Intel type 2716, requiring only a 
+5 V supply. While this is assuredly 
somewhat bizarre, there seems to be 
argument amongst the two companies as 
to who claimed the name 2716 first. It 
is definitely something that many will be 
in need to be aware of. 

David Marke 

Solar Dynamics Ltd 

3904 Warehouse Row, Suite C 

Austin TX 78704 

HOW TO STAY IN CIRCULATION 

I was somewhat astonished (an un- 
derstatement) to find, wrapped in the 
splendor of the March 1978 (I think) 
plain brown BYTE wrapper, an April 
1978 Playboy. Now don't get me wrong, 
I enjoy looking at lovely ladies; in fact 
it is one of my most time consuming 
hobbies. However, 1 can pick up Hef's 
rag anywhere in Ottawa, and right now 
my computer needs more tips on oper- 
ating than I do. So, if you would, I'd 
appreciate an issue of BYTE that 
matches the enclosed mailing sticker. 
Thank you. 

Kevin Szabo 

Box 86, Hillcrest Dr 

RR #1, Manotick 

Ontario CANADA KOA 2N0 

WHERE TO GETTECO 

Carl Helmers' editorial in the March 
1978 BYTE, page 6, was interesting to 
me, since the LSI-11 can run the RT11 
operating system, for which there is a 
version of real TECO (a superset of the 
old PDP6/PDP10 TECO) with most or 
all of the features he wants, plus ability 
to use floppies, etc. Sources for said 
TECO are available from DECUS for a 
minimal charge. I've worked on the 

Continued on page 120 




YOURS 
FOR ONLY 

^149.95 

Now, the first complete software 
oriented video system (theVB-IB.) is 
even morG versatile. The newly improved 
VB-1B Video Interface Board gives you 128 possible 
characters to play with. Graphics galore. Horizontal and 
vertical oscillators that operate within 1.6% of actual TV 
standards to get rid of wiggle, rolling and jitters. The 
VB-1B cuts snow by up to 50% and provides 8% left and 
right margins. And we'll give you a "Doodle" program so 
you can play around with graphic shapes on your own 
screen. Easy connection and adjustments . . , with the 
new VB-1B. Available— along with all our other S-100 
bus compatible products— either from your local 
computer store or from us diroctiy. 




r^r CI 



iu 



i.^.^L 



2116 Walsh Avenue 

B 95050 



Circle 335 on inquiry card 



A Division of Solid State Music 



Telephone (408) 246-2707 

|uly 1978eiBYTt Publications Inc 11 



,■4 



KIMER: A KIM-1 Timer 



Listing J: Combination digital cloc/i and timer program written for tine MOS 
Teclinology KIM-1 computer. The LED readout is used to display hours, 
minutes and seconds. 



Address 


Hexadecimal 


Label 


Op Code 


Comments 




Code 










00 00 


00 


SETHR: 


#00 






01 


00 


SETMIN: 


#00 






02 


00 


CNTR; 


#00 






02 00 


A5 00 


START: 


LDA 


SETHR 


Set starting time. 


02 02 


85 FB 




STA 


POINTH 




02 04 


A5 01 




LDA 


SETMIN 




02 06 


85 FA 




STA 


POINTL 




02 08 


A9 00 




LDA 


#00 




02 OA 


85 F9 




STA 


INH 




02 OC 


8D 03 17 




STA 


1703 


Set PB7 as input. 


02 OF 


A9 04 




LDA 


#04 


Set timer loop count. 


02 11 


85 02 




STA 


CNTR 




02 13 


A2 20 


TIMER: 


LDX 


#20 


Timer calibration. 


02 15 


CA 


DELAY: 


DEX 






02 16 


DO FD 




BNE 


DELAY 




02 18 


A9 F1 




LDA 


#F1 


Start timer. 


02 1A 


8D OF 17 




STA 


170F 




02 ID 


20 IF IF 


WAIT: 


JSR 


SCANDS 


Display current time. 


02 20 


2C 07 17 




BIT 


1707 


Wait for timer interrupt. 


02 23 


10 F8 




BPL 


WAIT 




02 25 


C6 02 




DEC 


CNTR 


Decrement counter. 


02 27 


DO EA 




BNE 


TIMER 


Finish second timeout. 


02 29 


F8 




SEP 




Set decimal mode. 


02 2A 


18 




CLC 




Clear carry. 


02 2B 


AO 00 




LDY 


#00 




02 2D 


A5 F9 




LDA 


INH 


Get seconds. 


02 2F 


69 01 




ADC 


#01 


Add 1. 


02 31 


85 F9 




STA 


INH 




02 33 


C9 60 




CMP 


#60 


Check if next minute. 


02 35 


FO 04 




BEQ 


MIN 


Branch if yes. 


02 37 


A2 19 




LDX 


#19 


Set delay count. 


02 39 


DO 23 




BNE 


SET 


Wait for next timer start 


02 3B 


84 F9 


MIN: 


STY 


INH 


Clear seconds. 


02 3D 


18 




CLC 






02 3E 


A5 FA 




LDA 


POINTL 


Get minutes. 


02 40 


69 01 




ADC 


#01 


Add 1. 


02 42 


85 FA 




STA 


POINTL 




02 44 


C9 60 




CMP 


#60 


Check if next hour. 


02 46 


FO 04 




BEQ 


HRS 


Branch if yes. 


02 48 


A2 14 




LDX 


#14 


Set delay count. 


02 4A 


DO 12 




BNE 


SET 


Wait for next timer start 


02 4C 


84 FA 


HRS: 


STY 


POINTL 


Clear minutes. 


02 4E 


A2 10 




LDX 


#10 


Set delay count. 


02 50 


18 




CLC 






02 51 


A5 FB 




LDA 


POINTH 


Get hours digits. 


02 53 


69 01 




ADC 


#01 


Add 1. 


02 55 


85 FB 




STA 


POINTH 




02 57 


C9 24 




CMP 


#24 


Check if next day. 


02 59 


DO 03 




BNE 


SET 


Branch if not. 


02 5B 


84 FB 




STY 


POINTH 


Clear hours. 


02 5D 


CA 




DEX 




Adjust delay count. 


02 5E 


D8 


SET: 


CLD 




Clear decimal mode. 


02 5F 


A9 04 




LDA 


#04 


Reset loop count. 


02 61 


85 02 




STA 


CNTR 




02 63 


4C 15 02 




JMP 


DELAY 


Start next cycle. 



Robert Baker 
15 Windsor Dr 
Atco NJ 08004 



This short program converts your KIM-l 
into a 24 hour digital clocl< and illustrates 
the use of the built-in timer for long time 
delays, and the use of instruction loops for 
shorter delays. The 7 segment displays 
are used for output, and are used in con- 
junction with one of the routines in the read 
only memory which drives them. 

To use the internal timer, 10 pin PB7 
of 6530-003 must be set as an input pin to 
allow testing of the timer interrupt. This is 
accomplished by setting bit 7 of the direc- 
tion register (location 1 703) to before 
using the timer. The timer is started by 
loading it with the desired delay count, and 
the address used determines the timer 
frequency and whether or not to enable the 
timer interrupt. Bits and 1 of the address 
select the timer frequency as 1, 8, 64, or 
1024 us per timer count while bit 3 enables 
the timer interrupt if set to 1 . 

This clock program uses the internal 
timer for a time delay of approximately 
250 ms. After four time delays (1 second), 
the current time is incremented by 1 and 
the timing cycle continues. Whenever the 
time count is being incremented, instruction 
timing delays are added where needed to 
keep all time delays constant for whatever 
program route is taken. An additional 
instruction delay is added within the 1 
second timer to calibrate the timer to 
exactly 1 second. If your system clock is 
slightly slower or faster, you may have to 
adjust the timer count (location 0219) for 
about 1 ms increments and the calibration 
count (location 0214) for 4 jis increments. 

To set the clock, enter the desired start- 
ing time hours in location 0000 and minutes 
in location 0001. To start the clock, set the 
program starting address (0200) and depress 
"GO" at the desired starting time (as set 
in locations 0000 and 0001). If the starting 
time is set as 0000 (hours and minutes), the 
program can be used to measure elapsed 
times for special applications by using the 
"ST" button to stop the program. For even 
fancier applications, you can add testing of 
an external switch to start and stop the 
clock. If you would rather have a 12 hour 
clock, simply change the contents of loca- 
tion 0258 from 24 to 1 2.» 






«: 
> 



* I 









12 



July 1978 O BYTE Publication! Inc 




Hie Computer for the Professional 



The 8813 was built with you, the professional, in mind. 

It quickly and easily processes cost estimates, payrolls, 

accounts, inventory, patient/ client records and much 

more. You can write reports, briefs, and proposals on 

the 8813's typewriter keyboard, see them on the video 

screen, and instantly correct, revise, or print them. 

Using the 8813, one person can process what would 

normally require many secretaries, several bookkeepers, 

and a great deal of time. And data storage takes a small 

fraction of the space used by previous methods. 



You don't need to learn complicated computer lan- 
guages. The 8813 understands commands in EngUsh. If 
you want to write your own programs, the 8813 includes a 
simple computer language, BASIC, that you can master in 
a few days. The 8813 slashes the professional's overhead. 
It's a powerful time and money-saving ally. Prices for 
complete systems including printer start at less than $8,000. 

See the 8813 at your local dealer or contact PolyMorphic 
Systems, 460 Ward Drive, Santa Barbara, California, 93111, 
(805) 967-0468, for the name of the dealer nearest you. 



PolyMorphic 
Systems 



BYTE July 1978 



13 




WliyApplel] 
St selling pei 



h the VTorlcTs 
l>iial comimter. 



rhich personal computer will be 
most enjoyable and rewarding for you? 
Since we delivered our first Apple® II 
in April, 1977, more people have chosen 
our computer than all other personal 
computers combined. Here are the 
reasons Apple has become such an 
overwhelming favorite. 

Apple is a fully tested and assembled 
mainframe computer. You won't need 
to spend weeks and months in assembly. 
Just take an Apple home, plug it in, 
hook up your color TV* and any cassette 
tape deck — -and the fun begins. 

To ensure that the fun never stops, 
and to keep Apple working hard, we've 
spent the last year expanding the Apple 
system. There are new peripherals, 
new software, and the Apple II Basic 
Programming Manual. And wait till 
you see the Apple magazine to keep 



owners on top of what's new. 
Apple is so powerful and easy to use 
that you'll find dozens of applications. 
There are Apples in major universities, 
helping teach computer skills. There 
are Apples in the office, where they're 
being programmed to control inven- 
tories, chart stocks and balance the 
books. And there are Apples at home, 
where they can help manage the family 
budget, control your home's environ- 
ment, teach arithmetic and foreign 
languages and, of course, enable you 
to create hundreds of sound and 
action video games. 

When you buy an Apple II you're 
investing in the leading edge of tech- 
nology. Apple was the first computer 
to come with BASIC in ROM, for 
example. And the first computer with 
up to 48K bytes RAM on one board, 
using advanced, high density 16K 
devices. We're working to keep Apple 
the most up-to-date personal computer 
money can buy. Apple II delivers the 
features you need to enjoy the real 



satisfaction a personal computer can 
bring, today and in the future. * 

& hi-resolutjon « 
graiihics.too. 

Don't settle for a black and 
white display! Connect your^ 
Apple to a color TV and 
BASIC gives you instant , 
command of three display 
modes: Text, 40h x 48v * 
Color-graphics in 15 colors,, 
and a 280h x 192v High 

Resolution " 
array that 
lets you plot 
graphs and 
compose ' 
3-D images. ^ 
Apple gives 
you the added- 
capability of combining 
text and graphics, too. 

Back to basics, and 
assembly lan^ua^ too. 

Apple speaks three languages: fast ^ 
integer BASIC, floating point BASIC ^ 
for scientific and financial applications, 
and 6502 assembly language. That's ■" 
maximum programming flexibility. And, a 
to preserve user's space, both integer 
BASIC and monitor are permanently 
stored in 8K bytes of ROM, so you < 
have an easy-to-use, universal language 
instantly available. BASIC gives you 
graphic commands: COLOR=, VLIN, ^ 
HLIN, PLOT and SCRN. And direct 
memory access, with PEEK, POKE 
and CALL commands. -• 

Software: Oufs and yotns. 

There's a growing selection of pre- 
programmed software from the Apple , 
Software Bank — Basic 
Finance, Checkbook, High 
Resolution Graphics and 
more. Now there's a User 
Section in our bank, to make 
it easy for you to obtain 
programs developed 







A 



/ 




^ by other Apple owners. Our Software 
Bank is your link to Apple owners all 
over the world. 

Alive with 
the sound 
of music. 

Apple's ex- 
clusive built-in 
speaker delivers 
the added dimension of sound to your 
programs. Sound to compose electronic 
music. Sound to liven up games and 
educational programs. Sound, so that 
any program can "talk" back to you. 
That's an example of Apple's "people 
compatible" design. Another is its light, 
durable injection- molded case, so you 
can take Apple with you. And the 
professional quality, typewriter-style 
keyboard has n-key rollover, for fast, 
error-free operator interaction. 

Apple is tiie 
proven computer. 

Apple is a state-of-the-art single 
board computer, with advanced LSI 
design to keep component count to a 
minimum. That makes it more reliable. 
If glitches do occur, the fully socketed 
board and built-in diagnostics sim- 
plify troubleshooting. In fact, on our 
assembly line, we use Apples to 
test new Apples. 

*Apple II plugs into any standard TV using / 

an inexpensive modulator (not included). 

*ln California, call 408/996-1010. 



4 



Apple peripherals 
are smart peripherals. 

Watch the far right column of this ad 
each month for the latest in our grow- 
ing family of peripherals. We call them 
"intelligent interfaces." They're smart 
peripherals, so you can plug them in 
and run them from BASIC without 
having to develop custom software. 
No other personal computer comes 
close to Apple's expandability. In addi- 
tion to the built-in video interface, cas- 
sette I/O, and four A/D inputs with two 
continuously variable game paddles, 
Apple has eight peripheral slots, three 
TTL inputs and four TTL outputs. Plus 
a powerful, state-of-the-art switching 
power supply that can drive all your 
Apple peripherals. 

Available now. 

Apple is in stock and ready for 
delivery at a store near you. Call us for 
the dealer nearest you. Or, for more 
details and a copy of our "Consumer's 
Guide to Personal Computers," call 

800/538-9696** 
or write Apple 
Computer, Inc., 
10260 Bandley 
Drive, Cuper- 
tino, CA 
95014. 






ulry card. 



g|npplG computer 



Programming is a snap! 
I'm halfway through Apple's BASIC 
manual and already I've programmed 
my own space wars game. 



Those math programs I wrote 
last week- 1 just rewrote them using 
Apple's mini-assembler and got them 

to run a hundred times faster 



New from Apple. 

Introducing Disk IP : 
instant access to your files. 

Our newest peripheral is Disk II, a 
high-deiisity 5V4" floppy disk drive for 
fast, lowcost data retrieval. It's perfect 
for storing large bodies of data such as 
household finances, address files and in- 
ventories; you can find any record in just 
half a second. No more searching through 
stacks of cassettes; with 
a few keystrokes, your 
system will load, store 
and run any file by 
name. 

Disk II consists of 




interface cards and fourteen drives, 
for control of nearly 1.6 megabytes of 
data, with no expansion chassis. The com- 
bination of ROM-based bootstrap loader 
and an operating system in RAM provides 
complete disk handling capability, includ- 
ing these special features: 

• Soft sectored • Random or sequential 
file access • Program chaining capability 

• Universal DOS command processor 
works with existing languages and monitor 

• Full disk capability in systems with as 
little as 16K RAM • Storage capacity : 
113 kilobytes/diskette. 

See Disk II now at your Apple dealer. 
Sold complete with controller and DOS at 
$495.t 

Peripherals in stock 

Hobby Board (A2B0001X), Parallel Print( 
Interface (A2B0002X), Communication Ii 
terface (A2B0003X), Disk II (A2M0004X 

Coming soon 

High speed Serial Interface, Printer II, 
Printer IIA, Monitor II, Modem IIA. 

' Price subject to change without notice. 

Circle 1 5 on inquiry c 

Apple's smart peripherals make 

expansion easy. Just plug 'em in ai 

they're ready to run. I've already 

added two disks, a printer and f^ 

communications card. 




The Second 
West Coast 
Computer Faire 



Photo 1: Some of the 

14,000+ crowd amble by a 
young hacker program- 
ming music on a Video 
Brain computer. 








By Chris Morgan, Editor 



San Jose was the place to be last March 3, 
4 and 5 for the Second West Coast Com- 
puter Faire. The Convention Center was 
easily able to handle the crowd of 14,169 
who came to see the latest developments in 
personal computing. 

A quick examination of some of the hun- 
dreds of manufacturers' booths revealed 
some trends: floppy disks are on the in- 
crease, with new models being shown or 
promised by Heathkit, Apple, Radio Shack 
and many others; more and more personal 
computers are now being offered with built- 
in floppy disks; peripherals and add-ons are 



2: Robot trials at 

mabyte booth, a 

attraction at the 

West Coast Com- 

re. 



,rd. 

id 
e 



it 



f 



13: IBM's booth, an 
[us addition to the 










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A"«^J£. 




to USl' '>!'>'■' ' 

.,. una to no,u'- VV'^' ^^^*;f;^\5, avaUabU' to pro^ > 
t.chnuaUss>sta>K. ^ ^^^^ ,,,,,,. uvr.ntK:^ 

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^.^0 ,v 8oao 



Photo 4: Ira Baxter's 
chess playing system dis- 
play, which competed in 
the Microcomputer Chess 
Tournament at the Faire. 




\ 






^ 



ri 




Photo 5: Apple Computer's new minifloppy 
drive. 




's Larry Weinstein displays Star Wars graphics. 



now available for a wide variety of computer 
buses. 

I enjoyed the many special features of the 
show, particularly the excellent computer 
generated art on display in the lobby. The 
microcomputer chess tournament proved to 
be one of the hits of the show. Larry Wagner 
from Atari presided over the 3 day battle of 
the processors, taking time out to give me a 
guided tour of the tournament. The level of 
play was impressive, and the winning pro- 
gram, called S ARGON, was a 16 K byte 
Z-80 assembler program written by a hus- 
band and wife team, Kathe and Dan 
Spracklen. It beat some highly touted com- 






♦ 



^jmmm 


U 

P^ 


--"— , t. 




^^^^^^^y 


^ 


fi 





^^^^^^^^^^ 



f^t 



. . . in software too! 



Hardware. Software. Peripherals. 
We've got the best in the business! 



P.O. Box 6528 Denver, CO 80206 (303) 777-7133 



Photo 7: Heath's new H27 
dual floppy drive, sched- 
uled to be available later 
this year. 




.1 
4 




Photo 8: Students from Mills College Center for Contemporary Music in 
Oakland demonstrate- a digital and analog hybrid music synthesizer system, 
one of many special exhibits at the Faire. 



petition. (A copy of the SARGON program 
is available for $15 postpaid from the 
Spracl<lens, 10832 Macouba PI, San Diego 
CA92124.) 

I was impressed with the professional ap- 
pearance of the show, which held its own 
with many of the established engineering 
and computing shows. The Third West Coast 
Computer Faire will be held this coming 
November 3, 4 and 5 in Los Angeles. Plan to 
see it if you can." 




Photo 9: Cromemco color 
video unit displays chess 
program at the Computer 
Room of San Jose booth. 



20 July 1978 (S BYTE Publicalions Inc 






NORTH STAR 16K RAM 
A star from our Horizon 














^ ■ri*'''''r"' 



"\^p 



aeisffiii 



-W- ■ I 



illiiiiiiiiiiiriiiimiiimiiiihliiiiiiimliilir 

• ..t..fiMti)iliM*>IMMI«IIIMIIMIMMIIIIII)M 



The North Star 16K RAM board is a star performer 
in our HORIZON computer. Just as important, it is the 
ideal memory for most other S-100 bus systems. No other 
RAM board can surpass the speed, reliability, and quality 
features of the North Star 16K RAM at any price. 

SPEED — The North Star 16K RAM is the fastest S-100 
bus memory board available. No wait states are required, 
even with a Z80 at 4MHz. And, of course, this outstand- 
ing 16K RAM will operate with both 8080 and Z80 proc- 
essors at 2MHz. Industry standard 200ns dynamic RAM 
chips are used. Invisible on-board refresh circuitry allows 
the processor to run at full speed. 

RELIABILITY — The North Star 16K RAM is designed to 
match the same high standards as our MICRO DISK 
SYSTEM and HORIZON computer. For example, all ad- 
dress and data signals are fully buffered. A parity check 
option is available with the 16K RAM for applications re- 
quiring immediate hardware error detection. If a memory 



error occurs, a status flip/flop is set and an interrupt can 
inform the processor. Or, if preferred, an error status 
light will go on. 

FEATURES —The North Star 16K RAM offers many de- 
sirable features. Addressability is switch-selectable to 
start at any 8K boundary. The board can perform bank 
switching for special software applications, such as time- 
sharing. Also, bank switching can be used to expand the 
amount of RAM beyond 64K bytes. Power consumption 
is minimal — the maximum power requirements are: 
.6A @ 8V; .4A @ -h16V, and .1A @ -16V. 

PRICES — $399 kit. $459 assembled, tested and burned- 
in. Parity option: $39 Kit. $59 assembled, tested and 
burned-in. 

Write for free color catalog or visit your local computer 
store. 



North Star * Computers 

2547 Ninth Street • Berkeley, California 94710 • (415) 549-0858 



Circle 285 on inquiry card. 



BYTE luly 1978 



21 




fe,*f;.'> .■:'-•■ 



Apfrficatlons Programs 
for your p®fs<mal comfHit^ 






INTRODUCING 
THE G2 PROGRAM 

LIBRARY. 

Now you doiTt hove 1o be a programmer 1o use 

WAIII' COIHIlllltPf I ^* ^^ there's a reliable, professional source of useful and entertaining 
F '^"' %%r ■ ■ ■!# W ■%#■ • programs for your personal computet The G2 Program Library from GRT 
unlocks the full power of your personal computet Without any programming knowledge on your part 
^ The G2 Program Library consists of applications programs pre-recorded on cassette tapes. A detailed manual 

with each cassette provides complete instructions. And G2 programs contain prompting instructions. So they're 
easy to use every step of the way. Just load the tape and 02 puts your computer to work. 

The first three G2 program tapes are available now: For exciting family games, get Beat the House. You'll find 
^i Blackjack, Craps, Roulette and Slot Machine programs, with truly random chances and realistic, casino-hlffi payoffs. 
Interested in your health? You'll want Ginic Biorhythms, Dieting and Longevity programs give you new 
perspectives in health and happiness, along with some pleasant guidelines to foUow. 

Need a better handle on your money? Buy Personal Finance. Qieckbook is a comprehensive program to 
balance your account and keep within your budget, while Best Choice is a novel way to make decisions based on 
the facts you know and the relative importance of each. Use it for everything from choosing a new car to 
If selecting your next stereo. 

Soon, every dealer that handles personal computers will stock the G2 Program Library. For the G2 dealer 
1^ nearest you, call us toll-free at 800/538-1770. (In California, 800/662-9810.) And if your favorite computer outlet 
doesn't yet offer G2, have him call the same numben 

G2 is the newest product Une from GRT, the world's largest independent producer of pre-recorded tapes. We've 
assembled a team of software specialists to produce the G2 Program Library. The fbest library of personal computer 
■> programs available. 

j^ Soon you'll see G2 program tapes in many other fields of interest Including advanced programs to challenge 

[ the interest of even the most serious computer usen The G2 IVogram 
i Library is available for most popular brands of personal computers. 
Just select the package marked for the computer you own. 

Start building your G2 Program Library now. 
And put the full power of your computer to 
. work for you. THE REASON 

^ YOU BOUGHT 

^ YOUR COMPUTER. I 



CRT 




A product of GRT Corporation 
Custom Products Division 

1286 North Lawrence Station Road r^^ „i„ i/io „ • _i nn 

Sunnyvale, California94086 Circle 148 on inquiry card. BYTE |uiy W8 23 



There's an Ohio Scientific 
dealer near you. 



ALABAMA 
M.C.S. Corp. 
Pelham Mall 
Pelham, AL 35124 
(205)663-1287 

ALASKA 

Scientific Business Instr's 
500 W. 27th 

Anchorage, AK 99503 
(907) 277-2650 

CALIFORNIA 

Expansion Techniques 
2534 Ganesha 
Altadena, CA 91001 
(213) 794-0476 

Shuey Aircraft 
1009 E. Vermont 
Anaheim, CA 92805 
(714)991-3940 

Olson Electronics 
11332 East South 
Cerritos, CA 90701 
(213)860-0060 

Computer Power 
1276 Via Rancho 
Escondido, CA 92025 
(714)746-0064 

Adventures in Computing 

8756 Warner 

Fountain Valley, CA 92706 

(714)848-8388 

Olson Electronics 
4642 West Century 
Inglewood, CA 90304 
(213)674-5740 

Olson Electronics 
Kearny Mesa, 4840 Convoy 
San Diego, CA 92111 
(714)292-1100 

Systems Engineering 

900 3rd Street 

San Francisco, CA 94107 

(415)777-3150 

Olson Electronics 
2125 El Camino Real 
Santa Clara, CA 95051 
(408) 248-4886 

COLORADO 

Total Data Systems 
125 Fairway Lane 
Fort Collins, CO 80521 
(303)491-5692 

Tricomp/Computer Country 
7115 N. Federal 
Westminster, CO 80030 
(303) 426-7743 



Delaware Microsystems 
92 East Main #1 
Newark, DE 19711 
(302) 738-3700 (after 7 PM) 

FLORIDA 
Olson Electronics 
5833 Ponce de Leon 
Coral Gables, FL 33146 
(305) 666-3327 

Olson Electronics 
1644 N. E. Second 
Miami, FL 33132 
(305)374-4121 

Calculator Place 
12 South Orange 
Sarasota, FL 33577 
(813)366-7449 

Olson Electronics 

6901 22nd Avenue, N, 

Tyrone Square Mall 

St. Petersburg, FL 33710 

(813)345-9119 

Olson Electronics 
1215 South Dale Mabry 
Tampa, FL 33609 
(813)253-3129 

GEORGIA 

Electronic Information 
120 Heatherwood 
Athens, GA 30601 
(404) 353-2858 



Secom Systems 
5241-F New Peach Tree 
Chamblee, GA 30341 
(404) 455-0672 

Olson Electronics 
2571 N. Decatur 
Decatur, GA 30033 
(404) 378-4201 

HAWAII 

Small Computer Systems 
3140 Wailalae 
Honolulu, HI 96816 
(808) 732-5246 



ILLINOIS 

American Microprocessors 

1100 E. Broadway 

Alton, IL 62002 

(618)465-4489 

Tech-Tronics 
714 S. University 
Carbondale, IL 62901 
(618)549-8495 

Adonis Computing 
2855 W. Nelson 
Chicago, IL 60618 
(312)463-0847 

Electronic Systems 
611 N.Wells 
Chicago, IL 60610 
(312)944-6565 

Olson Electronics 
4101 N. Milwaukee 
Chicago. IL 60641 
(312)545-7336 

Olson Electronics 

1734 0gden 

Downers Grove, IL 60515 

(312)852-9650 

A & H Associates, Ltd. 
2530 Crawford 
Evanston, IL 60602 
(312)328-2800 

No-Name 
2701 Grand 
Galesburg, IL 61401 
(309)343-6135 

CompuTermlnal Systems, Inc. 
1132 Waukegan 
Glenview, IL 60025 
(312) 724-3690 

Tek-Aids Industries 
1711 Chestnut 
Glenview, IL 60025 
(312)724-2620 

American Microprocessors 
6934 N. University 
Peoria. IL 61614 
(309) 692-5852 

American Microprocessors 
20 N. Milwaukee 
Pralrieview, IL 60069 
(312)634-0076 

Wysocki Electric 
3080 South Blvd. 
Rockford, IL 61109 
(815)874-4846 

Data Domain 
1612 E. Algonquin 
Schaumburg, IL 60195 
(312)397-8700 



INDIANA 

American Microprocessors 
146 N. Broad 
Griffith, IN 46319 
(219)924-7901 

American Microprocessors 
3602 East Washington 
Indianapolis, IN 46201 
(317)359-7445 

American Microprocessors 
2655 Irving 
Portage, IN 46368 
(219) 760-2278 

Computer Management 
610 Monroe 
LaPorle, IN 46350 
(219)362-5812 



Data Domain 
406 S. College 
Bloomington.lN 46401 
(812)334-3607 

Data Domain 
7027 N. Michigan 
Indianapolis, IN 46268 
(317)251-3139 
Data Domain 
10 N. Third 

LaFayette, IN 47902 
(317)423-2548 

Olson Electronics 
5353 N. Keystone 
Indianapolis, IN 46220 
(317)253-1584 

IOWA 

American Microprocessors 
102 E. 4th 

Waterloo, lA 50703 
(319) 296-2255 
John E. Chllds 
1201 E. Second 
Ohumwa, lA 52501 
(515)682-2165 

Microbus 

1910Mt. Vernon, S. E. 
Cedar Rapids, lA 52403 
(319) 364-5075 

KANSAS 

Barney & Associates 

425 N. Broadway 

Pittsburg, KS 66762 

(316)231-1970 

Technigraphics 
5911 Claredon 
Wichita, KA 67220 
(316) 744-2443 

KENTUCKY 

Data Domain 
3028 Hunslnger 
Louisville, KY 40220 
(502) 456-5242 

Olson Electronics 
117 Southland 
Lexington, KY 40503 
(606)278-9413 

Olson Electronics 
4137Shelbyville 
Louisville, KY 40207 
(502) 893-2562 

MARYLAND 

Systems Engineering 
1749 Rockvllle Pike #307 
Rockville, MD 20842 
(301)468-1822 

The Mathbox 

4431 Lehigh 

College Park, MD 20740 

(301)277-6828 

MASSACHUSETTS 
Bradshaw Enterprises 
18 Harborvlew 
Hingham, MA 02043 
(617)749-6844 

Computer Shop-Aircom 
288 Norfolk 

Cambridge, MA 02139 
(617)661-2670 

MICHIGAN 

The Abacus 

Route 1, Box 193 

Niles Road 

Berrien Springs, Ml 49103 

(616)429-3034 

Concept Engineering 
3706 Mallbu 
Lansing, Ml 48910 
(517)394-0585 

Great Lakes Photo 
5001 Eastman 
Midland, Ml 48640 
(517)631-5461 

Microcomputer World 
313 Michigan N. E. 
Grand Rapids, Ml 49503 
(616)451-8972 



Olson Electronics 

29121 DeQuindre 

Madison Heights, Ml 48071 

(313)546-0190 

MINNESOTA 

Custom Computer Systems 

1823 Lowry 

Minneapolis, MN 55411 

(612)588-3944 

Micro Business Sales 
4345 Lyndale N. 
Minneapolis, MN 55412 
(612)871-9230 

MISSISSIPPI 

Jack Fisher Sales 

100 Main 

Michigan City, MS 38647 

(601)224-6470 

MISSOURI 

The Computer Bit 

1320 S. Glenstone 

Springfield, MO 65804 

(417)883-2709 

Computer Place 
Rt. #4, Box 91 -D 
Joplin, MO 64801 
(417)781-1986 

Futureworld 
1909 Seven Pines 
St. Louis, MO 63141 
(314)434-1121 

Impact Systems 

Decker Building 

613 W. 3rd 

P.O. Box 478 

Lee's Summit, MO 66463 

(816)524-5919 

Norman Electronics 

402 Wall 

Joplin, MO 74801 

(417)724-0368 

MONTANA 

Linco 

P.O Box 2418 

Cut Bank, MT 59427 

(406)336-3117 

NEBRASKA 

Omaha Computer Store 
4540 South 84th 
Omaha, NB 68127 
(402) 592-3590 

NEW JERSEY 

Computer Corner 
224 Passaic 
Fairfield, NJ 07006 
(201)835-7080 

Computer Power 
235 Nutley 
Nutley, NJ 07110 
(201) 667-5502 

NEW YORK 

Associated Consultants 

33 Ogden 

East Williston, NY 11596 

(516)746-1079 

Brag Microcomputers 
19 (Cambridge 
Rochester, NY 14607 
(716)442-5861 

Computer Mart of N. Y. 

118 Madison 

New York, NY 10016 

(212)686-7923 

Microcomputer Workshop 
234 Tennyson Terrace 
Williamsvllle, NY 14221 
(716) 632-8270 

Ylngco 

Two World Trade Center 

Penthouse 107th Floor 

New York, NY 10048 

(212)775-9000 

OHIO 

Byte Shop 
2432 Chester 
Columbus, OH 43221 
(614)486-7761 



Johnson Computer 
123 W.Washington 
Medina, OH 44256 
(216)725-4560 

Lucas Office Equipment 

& Service 
869 E. Franklin 
Centerville. OH 45469 
(513)433-8484 

Olson Electronics 
69 West State 
Akron, OH 44308 
(216) 7620301 

Olson Electronics 
1994 Brittaln 
Akron, OH 44310 
(216)633-4338 

Olson Electronics 
3265 W. Market 
Akron, OH 44313 
(216)864-3407 

Olson Electronics 
2020 Euclid 
Cleveland, OH 44115 
(216)621-6387 

Olson Electronics 
6813 Pearl 

Cleveland, OH 44130 
(216)845-2424 

Olson Electronics 
6153Mayfleld 
Cleveland, OH 44124 
(216)449-2690 

Olson Electronics 
21850 Center Ridge 
Cleveland, OH 44116 
(216)331-4600 

Olson Electronics 
1975 Henderson 
Columbus, OH 43220 
(614)451-3245 

Otson Electronics 
7401 Market 
Southern Park Mall 
Youngstown, OH 44512 
(216)758-3828 



OKLAHOMA 

Accounting Systems 
2709 Orlando 

Oklahoma City, OK 73120 
(405)751-1537 

Gauger Engineering 
910 Orient 
Clinton, OK 73601 

Gauger Engineering 
3824 S. 79th East 
Tulsa, OK 74145 
(918)627-1064 



OREGON 

Flal Computer 
11013 S. E. 52nd 
Milwaukle, OR 97222 
(503) 654-9574 



PENNSYLVANIA 

Abacus Data Systems 

Route 8 

Reno, PA 16343 

(814)677-6502 

Olson Electronics 
5918 Penn 

Pittsburgh, PA 15206 
(412)362-1333 

Olson Electronics 
3405 Saw Mill Run 
Pittsburgh, PA 15227 
(412)881-0702 

Olson Electronics 
4778McKnlght 
Pittsburgh, PA 15237 
(412)366-7298 



TENNESSEE 

Computer Power of Memphis 
3065 James 
Memphis, TN 38128 
(901)386-9905 



Computer Powerof Oak Ridge 
800 Oak Ridge Turnpike 
Oak Ridge, TN 38730 
(615)4829031 

Smart Machine Mart Sd 

5151 Hlllson { 

Nashville, TN 37211 i 

(615)833-9773 A 



SOUTH DAKOTA 
Exe Engineering 
804 E. Lewis 
Vermillion, SD 57069 
(605)624-6411 



TEXAS 

Mr. Computer 

744 FM 1960 W, Suite E 

Houston, TX 77090 

(713)444-7419 



UTAH 

Small Computer Systems 

4450 Trinity 

Salt Lake City, UT 84120 

(801)967-7635 



VIRGINIA 

H/B Computers 

217 E. Main 

Charlottesville, VA 22101 

(804)295-1975 

Microsystems, Inc. 
5320 Williamson 
Roanoke, VA 24012 
(703) 563-0693 



WASHINGTON 

Ye Olde Computer Shoppe 
1301 George Washington 
Richland, V\iA 99352 
(509) 946-3330 



WISCONSIN 

Madison Computer Store 

1863 Monroe 

Madison, Wl 53711 

(608) 255-5552 

MicroComp 

785 S. Main 

Fond du Lac, Wl 54935 

(414)922-2515 

Olson Electronics 
3125 South 108th 
West Allls, Wl 53227 
(414)541-1406 



WYOMING 

Control Technology 
204 Crazy Horse Lane 
Gillette, WY 82716 
(307) 682-0300 



CANADA 

Omega Computing Ltd. 

Box 220 

Station P 

Toronto, Ontario 

Canada M5S 2F7 

(416) 425-9200 

Robo-Tronics 
509 16th N. W. 
Calgary, Alberta 
Canada T2M 0J6 
(403) 282-9468 

f IIROPF 

Pan Atlantic Computer 

System GmbH 
61 Armstadt 
Frankfurterstrasse 78 
West Germany 






^ 



24 



BYTE July 1978 



Circle 290 on inquiry card. 



The 

C2-8P 

* An exceptional value 
in personal computing 







ennuBuan n 




If you are interested in an ultra high per- 
[formance personal computer which can be 
fully expanded to a mainframe class micro- 
somputer system, consider the C2-8P. 

Features: 

Minimally equipped with 8K BASIC-in-ROM, 4K RAM, 
lachine code monitor, video display interface, cassette 
iterface and keyboard with upper and lower case 
|haracters. (Video monitor and cassette recorder optional 
<tras.) 

The fastest full feature BASIC in the microcomputer 
gdustry. 

Boasts the most sophisticated video display In per- 
pnal computing with 32 rows by 64 columns of upper 
jse, lower case, graphics and gaming elements for an ef- 
:tive screen resolution of 256 by 512 elements. 
'The CPU's direct screen access, coupled with its ultra 
yt BASIC and high resolution, makes the C2-8P capable 
|spectacular video animation directly in BASIC, 
-ully assembled and tested; 8 slot mainframe class 
procomputer, six open slots for expansion. Supports 
Jo Sclentific's ultra low cost dynamic RAM boards or 
I high reliability static RAMs. 



The C2-8P can support more in-case expansion than its 
four nearest competitors combined. 

The C2-8P is the only BASIC-in-ROM computer that can 
be directly expanded today to a complete business 
system with line printer and 8" floppy disk drives. 

It is the only personal class computer that can be 
expanded to support a Hard Disk! (CD-74) 

The C2-8P is the fastest in BASIC, has the most sophisti- 
cated video display and is the most internally expandable 
personal computer. Therefore, it should be the highest 
priced? 

Wrong: The C2-8P is priced considerably below several 
models advertised in this magazine. The C2-8P is just one 
of several models of personal computers by Ohio 
Scientific, the company that first offered full feature 
BASIC-in-ROM personal computers. 

For more Information, contact your local Ohio Scientific 
dealer or the factory at (216) 562-3101. 




1333 S. Chillicothe Road • Aurora, Ohio 44202 

-BYTE July 1978 25 



The C3-B 

by Ohio Scientific 

The worid's most powerful 

microcomputer system 

is far more affordable 

than you may thinic: 



STANDARD FEATURES: 

■ 74 million byte Winchester tech- 
nology disk drive yields mainframe 
class file access speeds and 
capacity. 

18 High level data file software 
makes high performance file struc- 
tures like multikey ISAM easy to 
use. 

S Triple processor CPU with 
6502A, 6800 and Z-80 gives the pro- 
grammer the best of all worlds in 
performance and versatility. 

■ Switchable and programmable 
CPU clocks at 1, 2 and 4 MHz yield 
maximum performance from each 
microprocessor. 



J 



1 
1 

-V 

\ 



■ The included 6502A based ex- 
tended disk BASIC by Microsoft 
out-benchmarks every micro 
available, including 4 MHzZ-80 and 
LSI-11 with extended arithmetic. 

■ 48K of high reliability static RAM 
is standard. 

■ High density 8" floppys provide 
program and data mobility from 
machine to machine. 

■ Completely integrated mechani- 
cal system with UL-recognized 
power supplies; continuous duty 
cycle cooling; modular construc- 
tion and rack slide mounted 
subassemblies. 



■ Based on a 16 slot Bus-oriented 
architecture with only 7 slots used 
in the base machine. 

■ Directly expandable to 300 
megabytes of disk, 768K of RAM in 
16 partitions, 16 communication 
ports, plus console and three 
printers. 

i» C3-B's have been in production 
since February, 1978, and are 
available now on very reasonable 
delivery schedules. 

The C3-B was designed by Ohio 
Scientific as the state of art in 
small business computing. The 
system places its power where it's 




needed in the small business 
environment; in the data files. The 
C3-B's advanced Winchester tech- 
nology disk, coupled with its smart 
controller and dedicated high 
speed memory channel, gives the 
C3-B data file performance com- 
parable with today's most powerful 
maxi-computers. 

The system can easily expand 
upward from single user to multi- 
user operation. Optional hardware 
and software include a real time 
clock and a 16 terminal (plus con- 
sole) real time operating system. 
Multiple terminal programs such as 
multi-station order entry can be 
programmed directly in BASIC. The 
system is super fast because multi- 
terminal I/O can be handled 
simultaneously with disk I/O due to 
the smart disk controller! 

By simply adding memory in the 
alternate partitions, the system can 
be expanded to full multi-tasking, 
multi-programming operation. The 
multi-terminal hardware supports 
both asynchronous and synchron- 
ous protocols in conjunction with 
terminals and smaller computers 
such as Ohio Scientific's BASIC- 
in — ROM and floppy disk based 
systems at transfer rates up to 
500K bits per second. 

■ The C3-B costs only slightly 
more than many floppy only com- 
puters but offers at least a thou- 
sand times performance improve- 
ment over such machines (50 times 
storage capacity multiplied by 20 
times access speed improvement). 

But what if your business client 
cannot justify starting with a C3-B? 
Then start with Ohio Scientific's in- 
expensive C3-S1 floppy disk based 
system running OS-65U. When he is 
ready, add the CD-74 big disk and 
directly transfer programs and files 
from floppy to big disk with NO 
modifications. 

That's upward expandability! 

*Rack as shown on right com- 
plete with 74 megabyte disk, dual 
floppys, 48K of static RAM, OS-65U 
operating system and one CRT ter- 
minal under $13,000. 

Multiple terminal systems with 
printers and applications software 
are priced in the mid-20's. 



1333 S. Ghillicothe Road • Aurora, Ohio 44202 

BYTE luly 1978 27 




Photo 1: The Axiom EX800 printer. It uses special aluminized paper; when a 
tiny electrical spark jumps from the print head to the paper, the layer of 
aluminum is burned off revealing the next layer which is darkly colored. 
Printing speed is a maximum of J 60 characters per second including upper 
and lower case letters. The printer allows 80 column page width and quad- 
ruple width characters. 



The 
Axiom EX800 Printer: 

A User's Report 



--« i i I 






n r, :_. L- !^ - i_! ri 

-=1. ts i~ sj a^ T 



' ! M ki n o n 



!■ i U V i!> K Y ci a I! i_ d t T y h t -3 k I !i! T! 
-_! s --- 1 ! - i i ^ 5—= f- 5^-? r^- -== I 

_3 ri L m Ti O F' '^ r" :S "t 



Figure I: A sample printout of the Axiom EX800 printer. This sample was 
made by photographically reproducing the original silver colored paper image 
ata J:l scale. 

28 July 1978 © BYTE Publicjtions Inc 



R J Bosen 

POB93 

Magna UT 84044 



Some time ago I decided I needed a hard 
copy printer to make my computer system 
really useful, but as I looked over the possi- 
bilities on the market I concluded that every 
alternative was either too expensive, too 
slow, or too limited in capability for my 
needs (which included good legibility and 
lower case printing). 

Just as I was about to abandon my plans, 
I saw a press release concerning a company 
called "Axiom" and a printer that appeared 
to solve all of my problems. It was adver- 
tised at $660, could print up to 160 char- 
acters per second (including upper and lower 
case letters) with an 80 column page width, 
and offered double and quadruple width 
characters as a bonus. 1 immediately wrote 
to Axiom and was surprised to receive a 
thick information packet within a week. 

My first (and only) disappointment 
came as I discovered that the 80 column 
page width was squeezed onto a 5 inch 
roll of special paper which was a little hard 
to read, but other features of the printer 
looked promising enough to justify further 
investigation, so I experimented with the 
printout sample they sent me to see if ! 
could find ways around these annoyances. 
I went to a photocopy center and found 
it was quite easy to get very sharp copies 
which were much more readable than 
the original. I decided that if the narrow 
page width became a serious problem 
I could write software to split a wide page 
into two 5 inch columns and print a page 
in two passes. Experimenting with the 
photocopier confirmed the feasibility of 
this idea as I successfullly laid two 5 inch 
pieces of the sample printout side by side 
and obtained the illusion of a 9 inch page 
width. 

I phoned the desk at Axiom to place 
my order; ten days later the printer was 
in my hands. I opened it up to reveal 
an Intel 4004 processor controlling an 
electrosensitive printing mechanism that 
works with special paper, consisting of a 
layer of paper, a layer of ink, and an 
aluminum upper layer. The print head 
strokes across the paper and burns the 
aluminum off in tiny dots, exposing the 
ink underneath in patterns stored in the 
processor read only memory. The processor 
controls character size and line length, 
allowing very flexible mixing of character 
sizes anywhere on any line and giving 
automatic line feeds when the end of the 
line has been reached. Other benefits of the 



I 

3 



i 






*■ 
f 



t 



microprocessor control include a self-test 
feature activated by pushing a button on 
the back panel which prints a test pattern 
on the paper, and a convenient parallel 
interface with simple handshai<ing. A serial 
interface is optional. 

I found the documentation very complete 
and readable and had no trouble interfacing 
with my parallel data port and writing driver 
software in a couple of dozen bytes. Trying 
it out on line proved to be a rewarding 
experience; my interface and driver software 
worked the first time. I was finally able to 
try out the many ideas I had been consider- 
ing while waiting for shipment. I noticed 
the effect of the 1 28 character buffer that 
Axiom provided: short printouts require 
almost no processor time, as the parallel 
interface transfers data from the processor 
memory to the printer buffer very fast 
and the processor is immediately freed 
to do other jobs. I was pleased with the 
quietness. It is not as loud as a Teletype 
even though it is about 14 times faster. 
It didn't take me long to discover the 
buzzer that can be activated by a special 
character, and I have learned to use it for 
special effects in game programs even when 
the printer is not needed. 

The only problems I have ever had with 
this printer have been concerned in one way 
or another with the paper. This is not to 
imply that I have had a lot of problems. I 
haven't. But finding a supplier for paper was 
a problem for me in Salt Lake City. I called 
every paper supplier in the phone book and 
I couldn't get anyone to even recognize the 
existence of "electrosensitive" paper. Fortu- 
nately, within a few weeks I found myself 
in DePere Wl repairing a computer system 
for my employer, and while there I took a 
tour of the Nicollet Paper Company, where 
the electrosensitive paper is made. They sold 
me a case of 24 rolls of the special paper at 
about $3 a roll and let me look at some of 
the experimental paper they are developing 
for use by electrosensitive printers. This new 
paper is much whiter than the silver grey 
originally shipped to me and I am anxious 
to see it introduced in production quantities. 

I am very pleased with the Axiom EX800 
printer, and I recommend it to anyone who 
needs a printer of this nature. Incidentally, 
Axiom also has a similar printer with a 
graphics capability that may be of interest 
to experimenters. You can obtain more 
information by writing to Axiom Corpor- 
ation, 425 E Green St, Pasadena CA 911 01 .■ 




The LFD-400 is ready to plug in and run 

the moment you receive it. 

Nothing else to buy! Not even extra memory! 

YOU GET: 

O The popular ShugartSA 400 minifloppy™ drive. Drive alignment 

is double checked by PerCom before shipment. 
O The drive power supply — fully assembled and tested. 
Q LFD-400 Controller/Interface— plugs into the SS-50 bus • 

accommodates tfiree 2708 EPROMs • fully assembled and tested. 
O MINIDOS™ — the remarkable LFD-400 disk operating system on 

a 2708 EPROM • plugs into the LFD-400 Controller card • no 

extra memory required • no "booting" needed. 
O Attractive metal enclosure. 

O Interconnecting cable — fully assembled and tested. 
O Two diskettes — one blank, the other containing numerous 

software routines including patches for SWTP 8K BASIC and the 

TSC Editor/ Assembler 
O 70-page instruction manual — includes operating instructions, 

schematics, service procedures, and the complete listing of 

MINIDOS™. 
® Technical Memo updates — helpful hints which supplement the 

manual Instructions. 
® 90-day limited warranty. 

Minifloppy is a trademark of Sfiugart Associates. 
tvllNIOOS is a tfademarl( of PERCOM Data Company, Inc. 

The LFD-400 Is readily expanded to either two or ttiree drives. 
Write for details. Send for our free broctiure for more informa- 
tion about the LFD-400 Floppy Disk System and LFD-400 
software. 

To save you money, the LFD-400 Floppy Disk System is available 
only from PerCom. Because of the special pricing, group and 
dealer discounts are not available. 

MC and VISA welcome. COD orders require 30% deposit plus 5% liandling charge. Allow three 
extra weeks if payment is by personal check. The LFD-400 Floppy Disk System is available 
immediately. Allow three weeks for testing and transportation. Texas residents add 5% 
sales tax. 




PEFQOM 



PERCOM DATA COMPANY, INC. 

Dept B 318 BARNES 'GARLAND, TX. 75042 
(214) 272-3421 

PERCOM™ 'peripherals for personal computing' 



Circle 301 on inquiry card. 



)uly 1978©BYTE Publicitions Inc 



29 




COOK BOOK • ASSEMBLER • __ 
MONITOR • POCKET GUIDE • TAPES 
UNDERSTANDING MICROCOMPUTERS 
COOK BOOK • ASSEMBLER • EDITOR 
^OR • POCKET GUIDE • TAPES 
. ^II^NDING MICROCOMPUTERS 
ASSEMBLER • EDITOR 
OCKET GUIDE • TAPES 
NG MICROCOMPUTERS 
ASSEMBLER • EDITOR 
JCET GUIDE • TAPES 
MICROCOMPUTE 





Order your SCELBI Personal Computer Books and Tapes today! They are 
"must" Items for your collection. And, they make ideal special occasion gifts 
for that computer buddy too! 

f cEUi coNPunn 

CONIUUINO INC. 




Prices shown for North American customers. Master 
Charge, VISA, Postal and Bank Money Orders pre- 
ferred. Personal checks delay shipping up to 4 weeks. 
Pricing, specifications, availability subject to change 
without notice. IMPORTANT! Include 750 postage/ 
handling for each item delivered by U.S. Mail Book 
Post Office Box 133 PP STN, Department B, MilfOrd, CT 06460 Rate; or $2 for each item shipped First Class or UPS. 



i 



1 



BYTE July 1978 



■^ 



f^y 



SCELBTS 
8080 

STANDARD 



scan HBnin 

\ CltlKTIH MC. 



°""n and Skill to your ^« '- 

I ■.. . . ...^■..^ .:^.-.........H ^°"'^ computer. 



Scelbi's '8080' Standard Assembler assem- 
bles programs written in symbolic language 
for '8080'. Describes operation of assembler. 
Detailed discussions of all major routines. 
Contains 2 completely assembled listings — 
hexadecimal and octal. Operating instruc- 
tions. Even includes routine for loading 
programs produced by the assembler. All 
memory references are labeled; can re- 
assemble to reside in ROM. (Some RAM 
required) $19.95. Optional object code on 
punched paper tape, specify 8080SA-OPT: 
$10.00. Optional commented source listing 
on punched paper tape, specify 8080SA-SPT: 

$39.00. 



Understanding Micro- 
Computers and Small 
Computer Systems, A 
profusely illustrated, 
easy-reading "must" 
book explaining funda- 
mental concepts behind 
operation of microcom- 
puters in simple English. 
Gives extra knowledge 
for reading and understanding computer maga- 
zines and manufacturers' literature. Makes you 
feel "at home" around computers. Accepted as 
the standard for the neophyte, you must own this 
300-page no-nonsense, easy-reading text. Includes 
simple-to-use glossary of key microcomputer- 
oriented words. Order now. Hard cover: $14.95. 
Soft cover: $9.95. 



SCELBI'S 
8080 



STANDARD 
EDITOR 



Kail ciartTH 
I CHsatTiu lie. 




Scelbi's '8080' Standard Editor is an efficient 
way to edit text when preparing program 
source listings or other text material. 
Operates in 2 modes? Text Entry and Com- 
mand. Memory references labeled for easy 
reassembly into any general area of memory; 
e.g. reassemble to reside in just IK of 
ROM. (Some RAM required) $12.95. 
Optional object code on punched paper 
tape, specify 8080ED-OPT: $6.00. Optional 
commented source listing on paper tape 
too. Specify 8080ED-SPT, $20.00. 



SCELBTS 
8080 



STANDARD 
MONnOR 



Kllll tIBPIIH 
t CmMTIH lie. 



Scelbi's BUtJU Stantiara ivionitor. Describes 
"Monitor Control" package to control oper- 
ation from external "keyboard". Routines to 
examine and modify memory locations, CPU 
registers, continuous 2-point "bug" status 
report, control bulk storage, I/O devices. 
And more. $9.95. Optional object code on 
punched paper tape, specify 8080SM-OPT: 
$5.00. Optional commented source listing 
on punched paper tape, specify 8080SM- 
SPT: $15.00. 




The '8080' Pro- 
erammer's Pocket 
'•■A compact 
3x41/2", ever- 
ready, instant 
reference for 
octal or hexadecimal codes, that 
explains instruction set in detail. 
Order your copy today. Keep one 
in your pocket. One near your 
computer, A "must"! Only 
$2.95 each. 



Circle 310 



°" '"Quiry card. 



ADVANCE NOTICE!!! 

Watch for the all new 

Scelbi's First Book of 

BASIC Programs! 

Coming soon! 

Want to be on Scelbi's exclusive 

mailing list? Want to know about 

upcoming Sceibi Books? Don't 

use the "BINGO" Card — but 

write us DIRECTLY. It identifies 

you as a "truly interested" 

customer who is worthy of 

special handling! 



\ 

J 



V 



Top-Down 

Modular 

Programming 



Albert D Hearn 
98 SW 13th Av 
Boca Raton FL 33432 



If you have done some programming, 
you know that it's one of the most en- 
joyable and satisfying parts of personal 
computer use. The very thought that the 
vast power in the small system's processor 
is limited only by the program that you 
write for it is tremendously exciting. 

If you are new to the computer game, 
the programs you have written up to now 
have probably been relatively small and 
uncomplicated, but you have developed 
a lot of experience and confidence from 
them. Most likely you haven't used any 
particular technique in designing and writ- 
ing your programs: you have probably 
approached program design in an informal 
way and relied upon your good senses to 
guide you in this unfamiliar task. You have 
probably also gained an understanding of 
the full capabilities of the instruction set 
and some of the little tricks (yes, ADDing 
a binary number to itself really does result 
in a left shift of one bit) which can be so 
useful. You are also capable of writing 10 
routines to do about any kind of data 
transfer you want. 

So now you are ready to do a program 
which does something really useful. The 
program you have in mind is going to be 
larger and more complicated than those 
you have done previously. While you might 
not expect this, your previous informal 
methods of designing and coding might 
possibly be inadequate and could cause 
you much grief if you attempt to use them 
on a larger program. 



Hopefully, I can help you prevent these 
kinds of difficulties by showing you in' this 
article an easy to use method of designing 
and structuring larger programs which can 
greatly simplify your personal efforts, 
regardless of complexity. 

The Concept 

Someone once said, "To solve a complex 
problem, simply break it down into a num- 
ber of less complex pieces, then proceed to 
solve it one piece at a time." This approach 
has been used for many years in the design 
and building of electronic equipment. It 
results in a "building block," or "modular" 
construction, where each block or module 
does some distinct part of the total function 
of the equipment. For instance, think of the 
last time you saw a diagram of a radio re- 
ceiver. It was probably in the form of a set 
of separate blocks representing the RF 
amplifier, mixer, IF amplifier, and so on. 
The blocks were all connected with flow 
lines showing the sequence in which each 
equipment module processed a signal coming 
from the antenna. The diagram enabled the 
reader to understand the function of the 
radio one module at a time, in relation to 
the whole radio. 

So how does the idea of using building 
blocks and solving problems piecemeal 
relate to the programming of personal 
computers? The answer is that these same 
ideas are very applicable to programming 
and have been in use in commercial pro- 
gramming for a number of years. There is 
no reason that good use of them can't be 
made in the amateur computer hobby also. 

Top-down Design 

Top-down design of microprocessor pro- 
grams requires that you first have a clear 
notion about what it is that you want the 
program to do. You should ask yourself 
questions like, "What function do I want 
performed?", "What input information is 
available?", and "What output information 
or action do I expect?" When you can 
answer these questions, you've actually 
completed the highest level of design. 



32 July 1978 IS BYTE Publicilions Inc 




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BYTE July 1978 33 



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34 BYTE July 1978 



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Figure 7: A basic top- 
down design diagram is a 
structure like tiiis. The 
number ofieveis may vary, 
and the number of boxes 
may vary, but the basic 
idea is given by this 
prototype. 



level I (highest) 



level 2 



level 3 (lowest) 



Figure 2: The first level of 
design is the act of saying 
"I want a program to do 
thus and so." Here "thus 
and so " Is defined to mean 
checkbook balancing. 



checkbook 
bank stmt 
deposit slips 
checks 



implied 
inputs 



balance 
checkbook 




implied 
outputs 



comparison ot checkbook 
and bank balances 
errors 
corrections 




The basic principle of top-down design 
procedure says that you start at a very high 
level of function definition and then pro- 
gressively expand that function into more 
and more detail until you're at a low enough 
level to begin coding your program. 
Actually, this is a very natural way to 
design solutions to any problem, but, for 
some reason, this method was very slowly 
applied to programming. The top-down 
method is different from bottom-up, where 
the concern is for coding and details before 
a real program design has been done. Bot- 
tom-up methods work on the "how" aspects 
of the program before the "what" aspects. 
An analogy of this method would be the 
building of a house, using no structural 
plans, by first laying down a convenient 
foundation and then gradually adding 
wood and stone until some desirable struc- 
ture has evolved. 

Let's take an example of a function 
that could be performed on a microproc- 
essor system for the purpose of illustrating 
the technique of modular, top-down pro- 
gram design. The function, monthly check- 
book balancing, was selected because it is 
a process that is familiar to most of us and 
it contains all of the elements which make it 
a good example. 

In order to design what you want the 
program to do, begin by drawing a multi- 
level design diagram like the one shown 
in figure 1. The diagram will describe what 
the program does at a number of different 
levels of detail, starting with the highest 



level which is a single block describing the 
overall function. The next lower level of 
blocks breaks the higher level function into 
a number of more detailed subfunctions. 
The next level takes those blocks and breaks 
them into even greater detail, and so on. 
An important point to remember is that the 
total function of the program is represented 
at each level. 

Figure 2 illustrates the first steps in the 
top-down design of your checkbook balanc- 
ing program. The first block simply states 
that the program will balance your check- 
book. There are no details in that block and 
it certainly doesn't invite coding at this 
point in the design. For input, you know 
that you will have your checkbook entries, 
monthly statement from the bank, deposit 
slips and cancelled checks. The output you 
want is a comparison of your checkbook 
balance (adjusted for recent deposits, ser- 
vice charges and outstanding checks) and the 
balance shown on the bank statement. You 
also want to know where any errors were 
made and what corrections are required. 

The second level of design, shown in 
figure 3, breaks the first level block into 
three major subfunctions. Although this sub- 
division could have been done differently in 
terms of the content of the second level 
blocks, the sum total of those functions 
always adds up to the entire function of the 
program. The idea is that you start the 
process slowly and don't attempt to develop 
too much detail too soon. Keep the number 
of subfunctions small, five or fewer, under 



July 1978 O BYTE Publications Inc 35 



Figure 3: Once the first 
level of design has been 
determined, the next level 
is specified by breaking up 
the task into parts which 
are fundamentally inde- 
pendent of one another. 
Here, checkbook balancing 
is viewed as three separate 
modules of function. 





balance 
checkbook 
































balance 
deposits 




bolance 
checks and 
charges 




compare bonk 
and checkbook 
bolonces 



( stort j 



match deposits 
in checkbook 
against bank 
statement 



adjust bonk 
balance for 
any late 
deposits 



match concelled 
checks to check- 
book entries and 
bonk statement 



adjust check- 
book balance 
for any bonk 
charges 



adjust bank 
balance for 
any outstand- 
ing checks 



compare bonk 
balance to 
checkbook 
balance 



determine any 
differences and 
correct 
mistakes 



C end J 



Figure 5: After the modu- 
lar structure of the ap- 
plication is determined in 
a hierarchy such as those 
exemplified In figures I to 
4, then attention can be 
given to sequencing of 
functions. This flowchart 
shows general level se- 
quencing of the checkbook 
balancing application. 



balance 
checkbook 



balance 
checks and 
charges 



match cancelled 
checks to check- 
book entries and 
bank statement 



adjust check- 
book balance 
for any bank 
charges 




adjust bank 
balance for 
any outstand- 
ing checks 



Figure 4: Carrying the process one step further, the next level is shown here for one of the 
branches of the structure of the programs. 



each function block. Don't worry about the 
order in which these subfunctions will be 
performed in your program. Remember, 
you're only concerned at this point about 
what is to be done, not how it is to be done. 

Next, take the design to the next lower 
level by further subdividing each of the 
second level blocks. Figure 4 illustrates a 
portion of this step. Just make sure that 
each subblock represents a complete sub- 
function and that the subfunctions at any 
level are equivalent to the program function. 

You might ask at this point, "How many 
levels must I go through?", or "How do I 
know when to stop?" There is no precise 
answer to these questions, although the fol- 
lowing guidelines should help. In general, 
you will find that you should stop when the 
lowest level of functions is so simple that 
you can easily write a program module to 
do each one. A module should be considered 
to have about 50 program instructions, or 
less. Experience will help you to know when 
you have reached this point. Also, you will 
find that the more complex the program, 
the more design levels you will need; general- 
ly, about three or four levels will be 
sufficient. 

Another method of determining if you've 



carried the design to a low enough level 
comes about almost automatically. If you 
are attempting to complete one of the lower 
levels and you find that the order of sub- 
function execution is becoming difficult to 
ignore, then you've probably gone far 
enough. Also, if you find that it is becoming 
necessary to show that program branching 
or decision making is required (top-down de- 
sign diagrams should show no decision logic), 
then you know that you have about the 
right level of design. You are now ready to 
start thinking about the how of your 
program. 

Modular Construction. 

If you try to make each block at the 
lowest level of your design diagram into a 
module, you might determine that some 
blocks are simple and can be combined 
into fewer modules. On the other hand, 
there will probably be blocks which would 
result in modules larger than the minimum 
size of 50 instructions we have established. 
In this case, take the blocks through one or 
more additional levels of design. 

Now decide what sequence the functions 
should be performed in. Begin drawing a 



36 luly 1978 © BYTE Publicitions Inc 



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BYTE lulv 1578 



37 



executive 



f start J 



return 




yes 



call 



return 



yes 



call 



return 



call 




yes 



call 



return 



r end j 




processing details 



call 



input and 
format all 
required 
data 



match concelled 
checKs to check- 
booK and bank 
statement 



subtract 
charges 
from 
checkbook 



subtract 
checks 
from bank 
balance 



compare 
bank 

balance to 
checkbook 



indicate 
amt. of mis- 
match and 
locate error 



processmg 
subroutine 
modules 



Figure 6: While the sequencing of the diagram shown in figure 5 is adequate, 
it is often usefui to explicitly partition all sequencing of execution in a 
separate module called the "executive" for the application. This flowchart 
shows a simple example of such an executive program which sequences the 
major operations of the application. 

flowchart showing the required sequence. 
Will each function be performed for each 
pass through the program? If not, add deci- 
sion blocks showing the conditions under 
which each such function is executed. Also 
add any function blocks which may be 
necessary to initialize data, clear tables, 
lO data, etc. 



Figure 5 shows a sequence of functions 
which results from the design of your exam- 
ple checkbook balancing program. Actually, 
the functions shown are probably too high 
level for this step, but for the sake of illustra- 
tion, the diagram should make the point. 

At this time, I would recommend that 
you consider making use of a special pro- 
gram structure called an executive routine, 
which offers some significant advantages. 
The executive is the main routine in the 
program and primarily contains calls to 
the function modules which do all the 
processing duties. It makes all decisions 
about the sequence of execution, it also 
contains the starting and ending points of 
the program. The objective of the executive 
is to concentrate most of the decision logic 
and common function of the program into 
a separate routine which becomes another 
program module. 

In this way, the function modules need 
not, and should not, make sequencing deci- 
sions. They should never directly pass con- 
trol to another function module. This should 
be done only through the executive. A func- 
tion module's only responsibility is to be 
given control by the executive, do its 
assigned job, and then return control back to 
the executive. Function modules are written 
in the form of subroutines using the call and 
return facilities of the programming language 
being used. They should also contain a 
generous sprinkling of comment statements 
to insure a high degree of understandability, 
as well as a well-defined lO interface to the 
outside world and the rest of the program. 

Figure 6 illustrates the final step in the 
modular, top-down design of your check- 
book balancing program. You have added an 
executive routine and some necessary house- 
keeping routines. You could begin coding 
the program from this flowchart by first 
writing the executive and the associated 
subroutine calls for each of the processing 
modules. By writing dummy subroutines 
which simply return control when they are 
called, you can test your executive for cor- 
rect operation without the need for the real 
processing modules. 

The next step, of course, is writing the 
processing routines. This is simplified by the 
design approach described in this article 
because it allows you to work on each routine 
as a separate unit which can be written and 
tested independently of all other routines in 
the program. When all routines are com- 
pleted, they simply plug into the executive 
to form a total program. Later, if you want 
to change the sequence of execution, add or 
delete functions, it can be simply a matter of 
manipulating modular routines. ■ 



38 |uly 1978 ® BYTE Publications Inc 



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of charges, credits and payments. Batch mode for monthly 

statements and aged schedules. 

Operators manual and disk, single copy $500.00 

INVENTORY PACKAGE Maintains current listing of stock 
items, master inventory listing with price and cost data. 
Operators manual and disk, single copy $500.00 

ORDER-ENTRY PACKAGE (Requires Accounts Receivable 
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Hours 9-4 daily Visit ournew showroom 

and Saturday Working units on display 

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Circle 355 on inquiry card. 



BYTE luJy 1978 39 



SYNCHROSOUND 



ENTERPRISES, INC.I 

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for Hardware and Software 



Everything you need in small computer systems with special emphasis 

on TERMINALS! Look at these units. ..compare price, quality, delivery, 

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LEAR SIEGLER ADM 3A TERMINAL 



• Full addressable cursor 

• Display format— 24 lines 
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• Communications rates— 75 to 
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ADM3A 

Kit 

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Assembled . 
Lower Case 
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ADDS REGENT 100 
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Display Format— 80 characters per line by 24 
lines. 25th line reserved for terminal status. Re- 
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and blinking are all standard features. 



Zio 



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OKIDATA MODEL 110 
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Fe'ed" 1349.00 

RS 232C 

Interface.. 260.00 



i4' 



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TELETYPE MODEL 43 PRINTER 

• 132 Characters per line 

• 110 or 300 Baud switch selectable 

• Full keyboard 

• RS 232C Serial Interface standard 



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OKIDATA MODEL 22 
LINE PRINTER 



125 lines per minute 
132-column print line 

• Upper/lower case 

• 8 different 
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Tractor Feed $2449.00 

RS232C Serial Interface. ..379.00 



DECWRITER II 

• 132 column printing 

• 10-30 CPS 

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$1495.00 



40 



BYTE July 1978 



SYNCHROMUND 



ENTERPRISES, INC.I 



CENTRONICS 
703 SERIAL 
PRINTER 



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CENTRONICS 761 PRINTER 

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• RS232, CCITT-V24, or 
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$2025.001 



KSR with Keyboard. 



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IMSAI 8080 MICROCOMPUTER 
• Powerful • Low cost • Easy to use 



IMSAI 8080 



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PCS-80/15 Kit 

699.00 



HAZELTINE 1500 
VIDEO TERMINAL 

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brightness levels 

• RS232 and 
current loop 
and much more"" 



Assembled 



$ 1 1 49.00 /Kit:^95.oo 



FLOPPY DISK 
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Digital Systems 
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SPECIAL BUYS 

Vista V80 Floppy Disk System $619.95 

Cromemco Z-2 Kit 565.25 

Compucolor8001 ColorComputer 2595.00 

IMS 16K Static Memory 525.00 

North Star Microfloppy Disk Kit 599.00 

North Star Horizon 1 Kit 1499.00 

North Star Horizon 2 Kit 1899.00 

Javelin 9" Video Monitor 159.95 

Livermore Modem Model 76 299.00 

Micropolis Model 1053MOD 2 1799.00 

IMSAI AP44-44 Col. Printer Kit 299.00 

TDLXitan Alpha 1 Assembled 939.95 



We carry a full line of the following: TDL, 
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SYNCHRO-SOUND ENTERPRISES INC 

The Computer People 

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212/468-7067 TWX: 710-582-5886 

Hours 9-4 daily Visit our new showroom 

and Saturday Working units on display 

Dept. BBB BankAmericard • Master Charge 



Circle 356 on Inquiry card. 



BYTE July 1978 41 



Who's Afraid of Dynamic Memories? 



It is not necessary to re- 
fresh euery cell of the 
dynamic programmable 
memory individually, but 
only the rows of the 
memory matrix. 



(Conversation overheard in local com- 
puter store): 

Customer: What's the difference be- 
tween static and dynamic memory? 
Salesman: Static memory worlds and 
■ dynamic memory doesn 't. 

It is unfortunate that the dynamic 
memory has had a rocky start in the small 
systems world, but it is not really surprising. 
The dynamic programmable memory is a 
part generally avoided by most designers 
because it is not nearly as simple to use as 
static memory. But taking the extra trouble 
and design care can pay handsome cost and 
performance dividends, since the dynamic 
memory is inherently a lower cost part than 
its static counterpart (by present standards 
of technology). 

The purpose of this article is to remove 
some of the mystery about dynamic mem- 
ory parts. In order to best cover all the 
trade-offs involved in a dynamic memory 
design, the discussion centers around the 
design of an actual dynamic programmable 
memory with the following specifications: 

1 . 32 K bytes on one card. 

2. Altair (S-100) bus compatible (an 
elusive specification, as we'll see later). 

3. Refresh mechanism invisible to the 
processor. 

4. Lowest power dissipation possible 
with current integrated circuits. 

5. Full speed operation in a 2 mHz sys- 
tem (no wait states). 

6. Foolproof operation: refresh main- 
tained despite halted processor and 
direct memory access operations, 
interrupts and prolonged wait states. 



Note: A commonly seen misnomer is the abbreviation "RAM" used to 
refer to a typical volatile programmable memory part such as those dis- 
cussed in this article. RAM stands for "random access memory, "which is 
descriptive of any memory part which addresses a unique memory cell 
given a set of binary inputs. A "read only memory " for example is also a 
random access memory, yet it is quite different In function from the vola- 
tile programmable memories. Thus in reading advertisements and manu- 
facturers' literature, be aware that the term RAM as used really means 
"volatile programmable memory, " a resource for the programmer who 
uses the system. . .CH 



Lane T Hauck 

Director of Research and Development 

Noval Inc 

8401 Aero Dr 

San Diego CA 92123 



Figure 1 is the usual starting point in any 
discussion of programmable memory. It is 
shown here only to point out that the static 
programmable memory cell uses six MOS 
transistors, while the dynamic cell uses only 
one (end of cost advantage argument). 

The dynamic programmable memory ceil 
uses a charge storage technique to store digi- 
tal information. The capacitor C^- in figure 
lb is charged for one logic state and dis- 
charged for the opposite state. Capacitors, 
being what they are, don't hold charge for- 
ever (due to leakage), so the cell shown 
works fine, but only for a few milliseconds. 
After that, the charge decays below a usable 
value. This is the reason for the mechanism 
called refresh. A refresh operation reads the 
value of the charge on the capacitor, ampli- 
fies it to its initial value, and dumps it back 
into the capacitor. 

Life would really be difficult if the de- 
signer had to implement the entire refresh 
operation (read, amplify, write) in a dy- 
namic memory system. Dynamic memory 
designers have made things simple by estab- 
lishing the following refresh "rules": 

1 . It is not necessary to refresh every cell 
in the dynamic memory individually, 
but only the rows of the memory 
matrix. 

2. A refresh operation is accomplished by 
simply accessing the required number 
of rows with any type of memory 
operation (read, write, or do nothing 
but set up the correct addresses ac- 
companied by a "strobe" or timing 
pulse). 

Programmable memories are organized 
in an XY matrix of rows and columns. 
The matrix is generally square, so it is 
possible to deduce the number of rows 
in the memory that must be accessed during 



42 July 1978 ©BYTE Publicitions Inc 



TARBELL SETS STANDARDS 

For Hobbyists and Systems Developers 

Sales to thousands of hobbyists over the past two years have proven the Tarbell Cassette 
Interface to be a microcomputer industry standard. Tarbell Electronics continues research and 
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CASSETTE INTERFACE 

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• 4 Extra Status Lines, 4 Extra Control Lines 

• 37-page manual included 

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• Full 6 month warranty on kit and assembled units 




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capacity of 256K bytes. 

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• Gold plated edge pins 

• Takes 33 14-pin ICs or 

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• ALTAIR/IMSAI compatible 
Price: $28.00 



For fast, off the shelf delivery, ail Tarbell Electronics products may be purchased from computer store dealers 
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' ALTAIR is a trademark/ tradename of MITS, Inc. 
CP/M is a trademark/tradename of Digital Research 



20620 South Leapwood Avenue, Suite P 
Carson, California 90746 

(213) 538-4251 




Circle 360 on inquiry card. 



BYTE luly 1978 43 



VDD 



(a) 



ROW SEL 




(b) 






CC 



Figure 1 : Comparison of static and dynamic memory cells. The static mem- 
ory cell (figure la) Is actually a flip flop (or bistable multivibrator) made up 
of six MOS transistors and capable of storing one bit of information. The 
dynamic memory cell (figure lb) uses one MOS transistor and a capacitor to 
store one bit of information. The major differences between the two memory 
storage techniques are cost (dynamic memories are significantly cheaper than 
static memories) and the fact that dynamic memories must be "refreshed" 
regularly to maintain the charges on the capacitors. 



CESSOR ADDRESS 
LINES 


REFRESH 
COUNTER 








r MULTIP 


LEXER , 








A 


6 


MULTIPLEXER 


REFRESH 

ARBITRATION 

LOGIC 


CONTROL 


















ADDRESS LINES 
nYNAMir MTMnRY D.u 










ARf 


(AY 













Figure 2: Refresh implementation block diagram. Dynamic memory cells 
must be refreshed periodically, or the capacitors used to store the bits of 
information will discharge. Refreshing is done by simply accessing the cells in 
question with any type of memory operation (read, write, or do nothing but 
set up and strobe the correct addresses). Because dynamic memory cells share 
common lines, it Is necessary to access only the rows of the memory matrix. 
All dynamic memories are set up so that the row decoders are fed by the least 
significant address lines (AO thru A 5 for a 4 K part, for instance). The mem- 
ory address lines are fed by a multiplexer that selects either the A lines (proc- 
essor address lines) or the B lines (refresh counter lines) as directed by the 
refresh arbitration logic. The selected lines are then fed into the dynamic 
memory array. The refresh arbitration logic insures that the refresh opera- 
tions and the processor operations do not interfere with each other. 



a refresh interval. For example, a 4 K by 1 
bit memory is 64 by 64, so 64 memory 
cycles must be performed for refresh; a 16 K 
by 1 bit memory is 128 by 128 and requires 
128 refresh cycles. The specification for 
refresh interval is generally 2 ms. This means 
that all rows of the memory matrix must be 
"exercised" at least once every 2 ms. 

Hovk' do you knovk" v^'here the "rows" are? 
All dynamic memories are set up so that the 
row decoders are fed by the least significant 
address lines; for a 4 K part, this means the 
six low order address lines, or AO, A1, A2, 
A3, A4 and A5. During the refresh opera- 
tion, the remaining address lines A6 thru 
All are in "don't care" states. For a 16 K 
part, the seven low order address lines AO 
thru A6 constitute the row address lines. 

Figure 2 shows how refresh is accom- 
plished. The memory address lines are fed by 
a multiplexer that selects address inputs 
from multiple sources. When the A inputs 
are selected, the processor accesses the mem- 
ory; when the B inputs are selected, the 
refresh address counter accesses the mem- 
ory. The role of the refresh arbitration logic 
is to insure that the refresh operations and 
processor access operations do not interfere 
with each other. The block diagram in 
figure 2 shows a 2 input multiplexer. A later 
section of this article shows how the number 
of inputs may be expanded to accommodate 
a multiplexed address programmable 
memory. 

Some system designs allow the use of dy- 
namic memories without having to imple- 
ment any refresh circuitry whatsoever. The 
most common system of this type is a video 
system that uses raster scanning. In order to 
present a stable image on the video display, 
all information is stored in a refresh mem- 
ory. As the electron beam scans the screen, a 
digital address that identifies the beam posi- 
tion is developed by the video display's tim- 
ing circuitry and fed to the memory address 
lines. The memory thus sequences continu- 
ously through its addresses. This satisfies the 
refresh requirement automatically, since the 
refresh counter of figure 2 is in effect re- 
placed by the video display's counters. 

The 4 K dynamic memory is currently 
available in three different packages: 22 pin, 
18 pin and 16 pin. The survivor of the in- 
compatibility battle is clearly the 16 pin 
package, due largely to its superior design, 
low power and true compatibility between 
multiple sources. Ironically, the smallest 
package, the 16 pinner, was the easiest one 
to convert to a 16 K memory part. [Several 
manufacturers of personal computers take 
advantage of this to offer memory in differ- 
ent combinations of 4 K and 16 K byte 
blocks . . .CM/ We'll see how this was done 



44 



July 1978©BYTE Publicalions Inc 



The AJ 841 l/Q 
A completely 
refurbished IBM Selectrk 
ASCII terminal with RS232 
or parallel interface. 




FEATURES: 

• ASCII code. 

• 14.9 characters per second printout. 

• Speciolintroductory price — $995 
[regularly $1,195]. 75% discount tronn 
original price of new unit. 

• Serial RS 232 or 
parallel interface. 

• Order direct from 
factory 

• Documentation 
included. 

• 30-day warranty — 
ports and labor 

• Higti quality 
Selecthc 
printing. 



Full warranty information available upon request 



• Reliable, heavy duty Selectric 
mechanism. 

• Off-line use as typewriter 




AJ 841 WARRANTY AND SERVICE 
IS AVAILABLE IN THE 
FOLLOWING CITIES: 

Los Angeles/ Cincinnati 
Philadelptnia/ Detroit 
l-lGckensact</ Dallas 
Columbus / Houston 
Cleveland / Atlanta 
Son Jose / Chicago 
Boston / New York 
Wostiington, D.C. 

For further 
information call 
(408) 263-8520 

ANDERSON 
JACOBSON 

Anderson Jacobson, Inc., 521 Charcot Avenue 
Son Jose, Calrforma 95131 



HOW TO ORDER AN 
AJ 841 I/O TERMINAL 

1. Make cashier's check or money order 
payable to: 

ANDERSON JACOBSON, INC. 

Address your request to: 
Personal Computer Terminal 
ANDERSON JACOBSON, INC. 
521 Charcot Avenue 
San Jose, CA 95131 

2. Upon written notification, pick up your 
terminal at the AJ service office 
located in one of the above cities, 
Allow six to eight weeks for delivery 

3. A final check of your unit will be made 
at the local AJ service office at time of 
pickup. 

4. For warranty or repair service, return 
unit to designated service location. 

5. Available in U.S. only 



SELECT EITHER: 



Number of units . 



CLIP AND MAIL WITHORDER 



Interface: RS 232 n or Parallel D 
Keyboard: EBCD D or Correspondence D 
@ $995 each $ 



Sales tax at delivery location 

Shipping and handling $35 
each (excluding San Jose) 

TOTAL 



NAME 

ADDRESS - 
CITY 



. STATE . 



-ZIP. 



PHONE I 



Circle 10 on Inquiry card. 



BYTE )ulv 1978 



45 



The current wonder of the 
semiconductor world is 
the 16 K dynamic pro- 
grammable memory. 



when address multiplexing is discussed later 
in this article. 

The current wonder of the semiconductor 
world is the 16 K dynamic programmable 
memory. The 16 K dynamic memory part 
that provides the prototype for the industry 
is the MOSTEK 1V1K4116. This is the part 
that virtually all semiconductor memory 
makers are laboring to emulate, due to its 
high performance and low power. Intel is 
another large supplier of 16 K dynamic 
memories in the form of the 2116, but the 
2116 dissipates much more power than the 
4116 and is not truly compatible with the 
4116 type part which the rest of the indus- 
try is lining up behind. Intel will shortly 
have a newly designed part that performs 
like the 4116. Texas Instruments is also in 
the process of redesigning their 16 pin part 
to perform like a 4116. 

The 16 K dynamic memory is in high 
demand these days, and the suppliers have 
not begun to meet the demand. This spells 
bad news for the experimenter, because 
prices will remain high (^20 to $30 each 
even in high volume) until the suppliers 
catch up to the demand. The day the 16 K 
chip becomes a "jellybean" part, such as the 
2102, is probably about two years off. 



There is, however, a sneaky way that the 
16 K part can be used economically today. 
Like all integrated circuits, the 16 K part 
undergoes thorough testing before it is 
packaged and sold as a part. The die size of 
the 16 K part is so large that the probability 
of something being wrong with one or a few 
array cells is fairly high. Clever manufac- 
turers (presently MOSTEK and Intel) are 
taking the parts which have problems as a 
16 K part, and retesting them to see if either 
of the two 8 K halves of the array function 
perfectly. And they do indeed find many 
parts which are perfectly acceptable 8 K 
parts. These parts are not factory "rejects": 
they meet all specifications for the 16 K 
device, but you can only use half of the part. 
Two part numbers specify the devices and 
tell the designer that a particular address 
line (AO) must be always high or always low. 
This permanently selects only the "good 
half." 

If you look closely at some of the current 
dense Altair (S-100) bus compatible memory 
boards, you'll see these devices (Intel calls 
theirs the 2108; MOSTEK's is the 4115). 
This type of part makes everybody happy. 

Continued on page 140 



^ 



> 



RAS 



CAS 



"IHC- 
V|L - 



ADDRESSES 



WRITE 



'OUT 



K 



'RAS 



'^RCD • 



n: 



••RAH 



ROW 
ADDRESS 



COLUMN 
ADDRESS 



Irsh 
'gas 



A 



'.rj' 



m 



TTMMUm 



■ rcs 



\ 



'RCH 



"OH - 
VOL- 



OPEN 



-c 



VALID 
DATA 



'off 



> 



Figure 3: Dynamic memory timing for tfie l\10STEK /VIK4176 16 K dynamic memory (Courtesy MOSTEK). Tlie foilowing 
steps are necessary for a memory cycie: set up tiie low order 7 bit address on tfie address line (for tiie case of the 16 K memory) 
by setting tiie address multiplexer to state 2; wait for tiie address lines to settle; drop the row address strobe (RAS) line to the 
low state to latch the low address into the port; wait the "row address hold time"; set up the high order 7 bit address on the 
address lines; finally, drop the column address line to the low state, which latches the high address into the port. 



<•: 



46 July 1978 © BYTE Publicilions Inc 



GET THE 



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It discusses the Pros and Cons of each system in No Uncertain Terms and takes a 
straightforward look at the micro computer industry as it relates to YOU. 

Written especially for the layman in a language he can understand. Profit from the 
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Includes hundreds of references. 

Table of Contents 

1 . Introduction 

2. Don't get hung up on the chips 

3. Which category do you fit into 

4. Now -About the Hardware 

5. Peripherials that plug in? 

6. What? No Software! 

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8. Addresses 



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which go parcel post. Foreign orders add 
$4 for air shipment and make payable in 
U.S. funds. 

BYTE luly 1978 47 



^ 



Antique Mechanical 
Computers 



Part 1: Early Automata 



Dr James M Williams 

58 Trumbull St 

New Haven CT 06510 



There is a high technology 

in every age, not just our 

own. 



My purpose in writing these articles Is to 
remind computer enthusiasts that there is a 
high technology in every age, not just our 
own. Described herein are some of the 
stellar accomplishments of earlier times. The 
technology of electronics is merely the latest 
link in a continuous chain of technological 
developments spanning 20,000 years. Before 
that, there was a mechanical technology. 

Part 1 of this three part series describes 
some highlights in the development of auto- 
mata up to the 18th century. Part 2 contin- 
ues with 18th and 19th century develop- 
ments, and part 3 concludes with a descrip- 
tion of Torres' 1 91 1 chess automaton. 

I am not going to speak here of those in- 
candescent moments long ago when the 
truly great and critical achievements of 
mechanics were discovered: that day when 
an ancient man hooked a stick under one 
large stone and over another to invent the 
lever. Nor will I consider the wheel, which, 
however it came about, multiplied mechan- 
ical possibilities so manyfold (pulley, cam, 
gear, crank, escapement) that as the know- 
ledge spread humanity was irrevocably 
changed. We simply do not know the story 
of mechanical knowledge and its spread, so 
we must spin scenarios instead of histories. 
We will also have to concentrate on high- 
lights, since an exhaustive treatment of 
mechanical computers would fill many 
books. 

We do know most of the latest chapter, 
however. It has taken place in the past 
350 years, beginning in Renaissance times, 
flourishing in the Industrial Revolution, 
and finally levelling off in the early years 
of this century. The mechanisms that are 



now commonplace were being born back 
then, and what exciting times they must 
have been. Glance through a compilation 
of mechanisms and note the dates of first 
appearances in machinery. You will be sur- 
prised to see how many basic movements 
date from two centuries ago. And with study 
and application, a man could learn them, 
make them his own, and employ them in 
mechanisms of his own. Consider the thrill 
of the obscure local blacksmith in, say, 
Saxony 400 years ago who copied in wood 
the mechanism of the town clock's striking- 
jack — the clock, a wonder that was the 
envy of other towns, imported at great 
expense from Italy — and discovered for 
himself the means of transforming rotary 
motion into intermittent linear motion, via 
a cam. (Medieval cathedral clocks generally 
had a life-size figure, man, angel, or devil, 
which carried a mace to strike hours on a 
bell: the "striking-Jacques" or "striking- 
jack.") Imagine the challenge and excite- 
ment in realizing that one could construct a 
clock that would strike noon fairly consis- 
tently when the shadow of the church 
steeple touches a particular joint of flagstone 
in the village square. Could one compress 
this wonderous mechanism into a container 
small enough to carry, and be able to see 
the time whenever he wished? Could one 
construct a clock for the pocket? 

The first ones showed up around 1650, 
bulky as an ostrich egg and not much 
better at keeping reliable time. A little over 
two centuries ago a carpenter from York- 
shire, England, James Harrison, who had 
taught himself mechanics over a period of 
30 years, constructed his fourth highly 



48 luly 1978®BYTE Publicitionsinc 






COMPUTER 






Js 



^'J(n.- 




■// 



'^n-i 



>»t, 



For Homeowners, Businessmen, Engineers, Hobbyists, Doctors, Lawyers, Men and 



mjii9. 




Vol. 



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through the program {most 
contained right in their source code,. - ^^^ ^m. » 

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Inverse-transforms, Windowing, Stidmg Windows, simultaneous 
FFT's variable data sizes, etc and as a last word our software is: 

• Readable — as all of our programs are reproduced full size for 
ease in reading. 9 

• Virtually Machine Independent — these programs are wn'1 
in a subset of Dartmouth Basic but are not oriented for any 

particular system. Just in case your Basic might not use one o 
particular system. Just in case your Basic might not use o 
our functions we have included an appendix in Volume V wl 
gives conversion algorithms for 19 different Basic's; that's right, 
just look it up and make the substitution for your particular 
version. If you would like to convert your favorite program in to 
Fortran or ApLor any other language, the appendix in Volume M 
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Photo 1 : The bird organ, a popular novelty of the 18th and 19th centuries. 
The device is a sophisticated automaton capable of imitating the sound and 
movements of a real bird: the wings flap, the head turns, and the beak moves 
to the accompaniment of assorted bird whistles. 



PIVOT POINTS 



PITCH 
PISTON 




VOLUME VALVE 



Figure 7 ; Schematic diagram of a typical bird organ mechanism. Two metal 
cams control the bird's voice: the far cam controls the pitch piston (located 
in the body of the bird whistle), and the near cam controls the volume valve 
(located inside the wind chest). 



accurate watch (chronometer) and won a 
prize of X20,000 from the British govern- 
ment in 1760. Determined to make the 
British Navy the master of the seas, the 
Admiralty offered a prize for a watch that 
would permit a ship to calculate its longi- 
tude with an accuracy of 60 nautical miles 
after being at sea for six weeks. (Latitude is 
relatively easy to calculate by accurately 
measuring the elevation above the horizon 
of any celestial body. Longitude is more 
difficult, and requires knowing the elevation 
at a time known relative to a fixed ref- 
erence, the zero meridian at Greenwich, 
England.) 

Mechanicians (an excellent name for the 
practitioners of this craft) chose to work in 
the field for much the same reasons we all 
choose a field today: because it was an 
absorbing and genteel means of earning a 
living, because it offered accomplishments 
one could show with pride, and because it 
was the area for future expansion, the grow- 
ing edge of the technology. Look at the 
legacy of machines they have left us: the 
Linotype, the typewriter and its relatives, 
the reproducing piano (and its less intel- 
ligent cousin, the player piano), clocks 
and watches of every description. They 
are all fine mechanisms, but most of them 
were perfected and essentially attained 
their present configuration 80 years ago 
and more. Electronic devices have displaced 
most of them. 

The flowering of mechanical technology 
had other branches that have now died 
out, though, leaving only accounts in books 
and a few decaying museum specimens 
of machinery which once stirred general 
admiration and brought fame to their 
creators: the Orrery, a clockwork model of 
the solar system, complete with moons, 
that once stood proudly in the exhibition 
room of every significant university; the 
dazzling variety of music boxes which once 
were found in every parlor; and so on. And 
who nowadays recalls the bird organ (see 
photo 1 and figure 1)? 

The bird organ was a mechanical device 
that produced a very close simulation of a 
bird's song; 200 years ago it was a very 
expensive and much cherished ornament 
in the parlor of every gentle home. I have 
seen electronic versions of circuits for such 
a device and have built one, but together 
with its transformer and loudspeaker it 
occupies most of the space in a small bird- 
house. A commercial version I purchased 
is slightly smaller, housed in a 3 inch plastic 
sphere. Around the year 1800 there was a 
bird organ made for sale to replace the 



50 luly 1978 <^ BYTE Publicalions Inc 



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In computer terms, the 
bird organ can be de- 
scribed as a spring driven 
power train controlled 
by a mechanical read only 
memory. 



head of a gentleman's walking stick. A 
hinged lid sprang open by a concealed 
catch, and out popped a minute feather 
covered bird model that opened its beak, 
spread its wings and sang. The entire device, 
except for its winding key, was housed in a 
gold ornamented cylinder 114 by 2 inches 
(3.8 by 5 cm) long. How's that for miniatur- 
ization? And I'll wager it made a better song 
than my blocking oscillator version. 

There were bird organs, or accounts of 
them, in antiquity. The Greeks used steam 
or air to drive whistles mounted in bird 
figures; the Arabs and Persians supposedly 
did the same. The mechanism was some- 
times a cluster of tuned whistles like a bank 
of miniature organ pipes, and this arrange- 
ment is found in a clock from 1 750, but the 
modern bird organ dates from about 1770 
and was likely devised as a means of teaching 
domesticated songbirds to sing. Soon minia- 
turized, it was incorporated into decorative 
objets d'art of all sorts: snuff boxes, per- 
fume flasks, table centerpieces (these often 
had small fountains of water and other dis- 
tractions built in), clocks, even watches 
(but these were very rare), and free standing 
forms. One delightful version of the latter, 
perhaps 9 inches (23 cm) high, depicts a 
lady seated at her desk and a bird on a perch 
pole nearby. Her hand is on a (mock) bird 
organ, which she cranks while her pet listens 
attentively. The bird then tries to copy the 
song, but makes errors, which she corrects 
by playing the lesson again so that the bird 
"learns" and repeats it accurately, with 
much enthusiastic flapping of wings, pivot- 
ing on the perch, etc. 

Large or small, the mechanism of bird 
organs was always the same (see figure 1): 
a main spring drove a gear train which oper- 
ated a bellows to compress air in a wind box, 
and another gear train drove an intricately 
cut cam which, via a piston, varied the pitch 
of a whistle connected to the air supply. A 
similar cam operated a valve to control the 
volume of the whistle tone. More gears drove 
cams that controlled the beak, wings, and 
pivoting actions via push wires ascending 
the perch pole and the bird's hollow legs. 
Songs of eight or nine species are to be 
found among bird organ mechanisms (some 
elaborate devices had double or triple songs), 
and the nightingale was most popular. 
Remember the fairy tale about the mechan- 
ical nightingale by brothers Grimm, about 
1855? It lived in a jewelled tree, and some 
devices were made in this form, but the 
objet d'art was perhaps most popular, 
being finished in enamel and gold and 
frequently decorated with precious stones. 
While bird organs were essentially one of a 



kind machines, there was a sort of produc- 
tion line for them maintained by the most 
famous makers, and many thousands of 
them exist in museums. A great many were 
exported from France and Switzerland to 
the Orient. They are still made, and, while 
expensive, they are no longer the luxury of 
rich men. [A German bird organ about the 
size of a pocket calculator Is currently avail- 
able for under $400 ... CM] 

In computer terms, the complete mecha- 
nism might be described as a spring driven 
power train controlled by a mechanical read 
only memory whose values are stored as a 
distance of the edge of the cam from the 
cam's center of rotation. In 45 seconds of 
singing, there might be a fair number of 
places where the notes sound, perhaps, six 
to eight per second (during a trill). 

Referring to figure 1 , if we have two cams 
which rotate in 45 seconds, and we allow a 
time division of ten samples per second, 
and if we allow eight bits of precision per 
sample, we would require 900 bytes of read 
only memory to simulate the control func- 
tions of these cams. 

A longer song, as in the tutorial automa- 
ton described above, might require three 
times as many bytes together with a smaller 
number to control bird and figure motion. 
This gives a total of 3 K bytes of mechanical 
read only memory divided unequally among 
several cams (something approaching the 
storage capacity of contemporary read only 
memory parts). 

A better way to look at this sort of mech- 
anism might be as a computer with analog 
storage (varying cam curves) and analog 
output (varying positions of the volume 
valve and pitch piston). Information is 
stored in the intricate curves of the cams. 
The information is fixed there for all time, 
or until wear or rust alter it, and may be 
recovered whenever it is needed by rotating 
the cam while the cam-follower rides on its 
periphery. It is in every way an "analog" of 
the desired sound, but it is not a recording, 
because it has been distorted in storage to 
suit the particular readout mechanism being 
employed (the cam-follower). (I have de- 
scribed the stored information as digital 
in order to facilitate the comparison; this 
has validity because of the relatively small 
number of analog positions and their re- 
solvability into bytes of restricted number.) 
Even in the 1770 to 1850 era the cam was 
not a new invention, but this application 
was novel. It was a benchmark in the field 
of mechanics. Storage of information had 
now become a tool of the mechanician, 
where formerly mere repetitive movement, 
the regular back and forth movement of a 



52 luly 1978 @ BYTE Publicitiom Inc 



clock's mechanism, was known to be 
available. 

With the possibility of storing informa- 
tion comes the possibility of crafting com- 
plex and seemingly nonrepetitive movement. 
If it is the desire of the builder of the mecha- 
nism, these movements may be arranged to 
mimic the movements of living organisms. 
This is the basis of more complex mechan- 
ical toys like the rabbit that walks about 
beating on a drum. (Incidentally, in 1880 a 
minute gold rabbit, perhaps an inch high, 
who also played his drum, was sold as a 
brooch. Not to mention a 3 inch gold 
caterpillar that sedately crawled its path, 
circa 1850.) 

However engaging, these were funda- 
mentally simple and regular movements 
that did not tax the designer. Mechanicians 
have constructed far more complex ma- 
chines designed to duplicate the most 
intricate and coordinated movements per- 
formed by living creatures and to produce 
an effect of illusory life for the few minutes 
the mechanism operates. Why would clever, 
dedicated people do such a thing? Why build 
an automaton? 

Machines That Imitate Life: a Rationale 

Until modern times there was a pervasive 
and unchallengeable view that the bodies of 
human beings were not fit subjects for in- 
vestigation. Death was the penalty for 
human dissection during the middle ages, 
except for rare occasions when the Church 
sponsored demonstrations of the corpses of 
criminals. Clearly, anything so sternly for- 
bidden must have been well worth investi- 
gating; could it have been that the secret of 
life lay concealed in the structure of the 
body? There were some who took the risk, 
and they always found that animal and 
human structure were very similar. Since, 
in the influential and respected view of Rene 
Descartes (1596-1650), animals were ma- 
chines that differed from humans chiefly in 
their lack of divine inspiration, it is easy to 
see the framework for a "mechanistic" 
view of living organisms. The notion held 
much appeal. It explained in terms that 
were comprehensible to the average edu- 
cated man how living creatures were con- 
structed by substituting mechanism for 
mystery. 

Popular expositions of science from the 
1890s right up to the 1940s typically de- 
picted drawings of a person cut away to 
reveal bellows and pump rooms in the chest, 
the chemical factory in the abdomen, the 
telephone switchboard in the skull, the 
pistons and gears in the limbs, and so on. 



I suggest that this conception of orga- 
nisms as chains of mechanisms, and the 
corollary, of a god as the divine watchmaker 
who constructed and set them in motion, 
was perhaps the most influential factor lead- 
ing to the construction of machines designed 
to imitate life. Note the variety of literature 
in which the attempt to create life is central 
to the theme: from ballads and fairy tales 
dating back to the beginning of language to 
Mary Shelley's Frankenstein (1818); from 
Offenbach's opera with the clockwork 
ballerina. Tales of Hoffman (1881), through 
countless science fiction works, to tales such 
as Shaw's Pygmalion. And of course there 
is recombinant DNA research, the leading 
edge of biochemical investigation at this 
moment where the purpose is, manifestly, 
to explore the mechanisms of life in living 
cells. The impulse is still there in us although 
the metaphor is different in different ages, 
and the mechanisms employed are de- 
pendent on available technology. 

Astonishing Automata 

About 1709, in Grenoble, the Edison of 
automata, Jacques de Vaucanson, was born. 
Little is known of his early life, except that 
he was something of a rake and a seminary 
dropout who disrupted affairs at the monas- 
tery by making wood and paper wings that 
flew about. But much is remembered of his 
automata, which, though they no longer 
exist, were the marvel of their age, the 
object of admiration by all gentlemen who 
saw them, and the envy of mechanicians ever 
since. 

Vaucanson was not a showman, but a 
philosopher and inventor. He often spoke of 
"moving anatomy," his expression for the 
concept that life, especially life in lower 
animals, was in fact a series of undirected 
movements (what we would today call 
"reflex movements"), and that by duplicat- 
ing the movements and actions of a live 
creature, one might succeed in duplicating 
the life of the creature. While such a notion 
seems absurd to us (it is, according to cur- 
rent understandings of the formation of 
ideas, magical, and therefore primitive) there 
is precedent for it from a character no less 
important than St Thomas Aquinas. Vaucan- 
son had a splendid opportunity to come 
across St Thomas's writings, since he lived 
in a monastery for perhaps 1 5 years. Books 
were expensive treasures in 1709, and mon- 
asteries were the main places where collec- 
tions existed. St Thomas's works would 
probably have been among them. In the 
Summa Theologica (Q13; Art 2; Reply 
obj 3; Part II) there is a passage: "Animals 



About 1 709, In Grenoble, 
the Edison of automata, 
Jacques de Vaucanson, 
was born. 



July 197aOBYTE Publications Inc 53 



show orderly behavior and are machines, as 
distinct from man who has been endowed 
with a rational soul and therefore acts by 
reason." 

If animals are orderly machines, it might 
be possible to make a machine that looks 
and behaves like an animal. If one took 



special pains to reproduce vital details like 
respiration, digestion and excretion, etc (so 
runs the argument), one would then have 
created the next best thing to a real living 
animal. 

Vaucanson arrived in Paris in 1735 at the 
age of 26 to pursue his moving anatomy con- 





AVEC PERMISSION | 

DU MAGISTRAT DE LA VILLE, | 

On expofera a la vue dn Pttblique les^. chefs etOeuvres Mechaniques du Celibre Mon- H 
fieitr VAUCANSON,. Membre de PAcademie Royale des Sciences de Paris, m 
qui confiftent en trois Figures Automates. S 

SC A V O 1 R: m 

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^ Canard vivant. m 

QR l^Es 3. Pieces qui ont fait meriter une Recompenfc a I'Authcur d*une Penfion de 8- m'"e & ?■ cent Litres par Ic Roy , Ji qui ont en- Sw 
Hi gag^ un grand nombre des Pcrfonnes de diftinflion a des longs & penibles Voyages pour les voir . marque micux Icur mcrite qu'un plus ^J 
^£ long detail. On Efpere que dans cette Ville un chacun fera charm^ de propter de Toccafion de les voir & qu'its en feront la dilTerence ^5 
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Figure 2a: Three automata invented by Jacques de Vaucanson in the mid-1 8th century. Shown 
are a flute player, mechanical duck, and a flageolet (whistle) and drum player. The novelty of 
these figures caused a sensation in their time (from an 18th century engraving, courtesy 
Bettmann Archive). 



54 luly l978SBYTt Publicjtionslnc 



A = FOUR FINGERS OF RIGHT HAND 
B" = THREE FINGERS OF LEFT HAND 




DISTRIBUTOR 



LOW PRESSURE 
MEDIUM PRESSURE 
— HIGH PRESSURE 



cepts. He promptly ran out of money. There 
is documentation to show he had the idea 
". . . of getting assistance by producing 
some machines that could excite public curi- 
osity . . ." as a means of raising funds. He 
excited plenty of public curiosity, for in 
1738 he simultaneously displayed three 
automata (see figure 2a). An automaton 
duck ". . . made of gilded copper who 
dtiiiks, eats, quacks, splashes about on the 
water, and digests his food like a living 
duck" was one, and a pair of automata 
musicians who played flute and drums were 
the others. 

The machines were life-size and were 
mounted on cubical pedestals about three 
feet on a side, which contained the bulky 
mechanism. They were unique and original, 
and they created a public sensation for 50 
years. To me, the flute player seems the 
most remarkable mechanism of the three. 
De Juvigny, a friend of Vaucanson's, wrote 
in 1777, "At first many people would not 
believe that the sounds were produced by 
the flute the automaton was holding. These 
people believed that the sounds must come 
from a bird organ or German organ enclosed 
in the body of the figure. The most incredu- 
lous, however, were soon convinced that 
the automaton was in fact blowing the flute, 



that the breath coming from his lips made it 
play and that the movement of his fingers 
determined the different notes. . . The pec- 
tators were permitted to see even the inner- 
most springs and to follow their move- 
ments." Figure 2b shows the mechanism in 
outline form. All that needs mention is the 
weight motor (not shown), and the fact that 
different weights were added to each bellows 
in the set of three to provide different pres- 
sures of air. High, medium and low pressures 
provided the designer with the possibility of 
playing notes loudly or softly in the lowest 
register, or of shifting the flute to a higher 
register by employing greater pressures. The 
distributor valve selected the correct pres- 
sure for a given note. 

Ihe illustration merely hints at the head 
mechanism, which must have been extremely 
complex. This description of flute playing is 
from the Encyclopedia Brittanica: "The 
flute is held sideways to the right of the 
player, who forms his lips to make an aper- 
ture and directs his breath stream across the 
mouth hole and onto its further edge, where 
it breaks up into eddies that alternate regu- 
larly above and below this edge and so excite 
the air column of the flute into vibration. 
Stability of the notes in the various registers 
and at different loudnesses is achieved by 



Figure 2b: Details of 
Vaucanson 's remarkably 
sophisticated flute player 
automaton. A music box- 
like drum with pro- 
grammed pins controlled 
the motion of the fingers, 
volume of air and shape of 
the mouth (made of 
rubber) so that the device 
actually played a standard 
flute. 



luly 1978 ; BYTL Publiialioni Inc 



55 



"(Vaucanson's mechanical 
duck) is the most admi- 
rable thing imaginable, a 
piece of human work- 
manship almost passing 
understanding." 



control of lip aperture, angle of breath im- 
pact, and breath force. The compass is three 
octaves. . . ." Vaucanson's complications 
came from his decision to use the true flute, 
blown from the side, and not a recorder, 
which is an air pipe instrument blown from 
one end like a pennywhistle or organ pipe. 
In both instruments, air column length is 
varied by closing the appropriate holes in the 
body. To some degree Vaucanson simplified 
his task by employing seven active fingers 
(instead of eight, the modern standard: or 
maybe his particular flute had only seven 
fingerholes), but he took on and overcame 
the challenge of providing means to produce 
the proper size of lip aperture and the 
proper angle of breath stream to mouth 
hole. It seems quite likely that Vaucanson 
used actual rubber, first seen in France in 
1736, in the lip mechanism, for there is evi- 
dence (in another automaton) that he knew 
how to fabricate rubber. 

Now, I can imagine a mechanism that 
would dilate and contract the aperture in a 
set of rubber lips, and vary somewhat the 
angle of a stream of air blown through the 
hole, but I have the considerable advantage 
of being able to draw on two centuries' accu- 




Figure 2c: Details of Vaucanson's mechanical duck, showing the intestine- 
like tubing within. The duck could drink, quack and splash about, and was 
able to eat, digest and eliminate food (from an 18th century engraving, 
courtesy Bettmann Archive). 



mulation of mechanical knowledge. Vaucan- 
son was starting from scratch, building a 
mechanism never before seen, to produce a 
motion never before defined, to perform a 
task never before attempted. That he suc- 
ceeded so well is astonishing; that he did it 
within 36 months is staggering. And remem- 
ber, he employed mainly hand tools. There 
was no local machine shop he could call on 
to mill a part. We have no record of where 
Vaucanson learned his mechanics, but his 
skills were prodigious. 

The combination tabor (drum) and 
flageolet (pennywhistle) player shown at the 
right in figure 2a was undoubtedly con- 
structed along similar lines; I have not seen 
an explanation of its mechanism. It would 
have been simpler, since the flageolet is 
easier to play than a flute (only four or five 
finger holes, blown from one end), and ma- 
chinery to make the right arm beat the drum 
would be relatively simple to figure out. It 
seems unlikely the two automata could have 
been so well synchronized that they played 
together. 

Vaucanson's Mechanical Duck 

It always startles me to read things like 
this anonymous appreciation of Vaucanson's 
duck: "It is the most admirable thing 
imaginable, a piece of human worksmanship 
almost passing understanding." I try to ac- 
count for the powerful attraction that con- 
structing simulacra of lower animals held for 
men 200 years ago. Still, it catches me off 
guard to see the adulation the duck evoked. 
Dr G C Beireis, the fourth owner of the ma- 
chine in 1785, rhapsodizes, "It was in this 
duck that Vaucanson's genius reached its 
highest point. I have still not got over my 
astonishment at this work. (He had seen it 
thirty years earlier.) One single wing con- 
tains more than 400 articulated pieces." I 
doubt we would feel that way today about 
an automated Scottie, say, but maybe ducks 
make better pets. 

It was, from all accounts, a singular like- 
ness to a duck, and here is what it did: 

After a light touch on a point on the 
base, the duck in the most natural way 
in the world begins to look around 
him, eyeing the audience with an intel- 
ligent air. His lord and master, how- 
ever, apparently interprets this differ- 
ently, for soon he goes off to look for 
something for the bird to eat. No 
sooner has he filled a dish with oat- 
meal porridge than our famished 
friend plunges his beak deep into it, 
showing his satisfaction by some char- 
acteristic movements of his tail. The 



56 July 1978 @ BYTE Publicilions Inc 



way in which he takes the porridge 
and swallows it greedily is extraordi- 
narily true to life. In next to no time 
the basin has been half emptied, al- 
though on several occasions the bird, 
as if alarmed by some unfamiliar 
noises, has raised his head and glanced 
curiously around him. 

After this, satisfied with his frugal 
meal, he stands up and begins to flap 
his wings and to stretch himself while 
expressing his gratitude by several con- 
tented quacks. But most astonishing of 
all are the contractions of the bird's 
body clearly showing that his stomach 
is a little upset by this rapid meal and 
the effects of a painful digestion be- 
come obvious. However, the brave bird 
holds out, and after a few moments we 
are convinced in the most concrete 
manner that he has overcome his in- 
ternal difficulties. The truth is that the 
smell which now spreads through the 
room becomes almost unbearable. We 
wish to express to the artist inventor 
the pleasure which his demonstration 
gave to us. (From Chapuis' book, 
Automata: Historical and Teclinical 
Study, see detailed bibliography in 
part 3 of this article.) 

Something here for everyone, isn't there? 
Passion, satisfaction, and a dash of slapstick. 
The mechanicians in the audience were 
dazzled by Vaucanson's skill in building a 
duck that could swivel its neck in every 
direction while sitting or standing; this does 
suggest some remarkable techniques for 
managing the pushwires ascending the legs, 
maybe even some internal mechanisms 
within the body. 

Probably written by Vaucanson and cer- 
tainly based on data only he could have pro- 
vided, the following passage from an article 
in a 1777 dictionary of science shows how 
proud he was of the internal mechanisms 
that caused grain to be ". . . digested as in 
real animals by dissolution and not by 
(grinding) . . . the inventor does not set this 
up as a perfect digestive system capable of 
manufacturing blood and nourishing juices 
to support the animal, and it would be un- 
fair to reproach him with this shortcoming." 
But it is clear how well he knew the 18th 
century idea that blood comes from food, 
and he implies he was trying to follow it. 
Indeed, in some accounts the body was 
covered by latticework so the interior 
mechanisms could be viewed as they did 
their job. Vaucanson had good reason to be 
proud, for the body contained his new 
invention, the rubber tube. Any machine 



capable of making that kind of smell had 
to be alive! 

One wonders what the "...chemical lab- 
oratory where the principal part of the food 
could be decomposed..." mentioned in the 
article might refer to. It may have been 
that his rubber tube intestine actually con- 
tained some chemicals or enzymes that 
attacked the starch in oat porridge, causing 
it "...to leave the body in markedly changed 
form." But there was hardly time enough in 
a performance of a few minutes to convert 
anything. More likely the operator between 
performances drained the stomach of its 
contents and loaded the nether-part of the 
intestine with the imitation duck dung that 
so impressed audiences. 

The duck and the two musicians probably 
made a good deal of money for Vaucanson, 
but because it was necessary to transport 
them to other capitals of Europe for further 
exhibition he sold them all in 1743 to show- 
men who took them to England, Russia, and 
finally to Germany. In St Petersburg in 1782 
the third owners tinkered with the mecha- 
nisms, interchanging parts so they would 
break if anyone else tried to show them. 
Dr Beireis had this partly repaired, but 
when Goethe viewed the duck in 1805, he 
found, "Vaucanson's automata were para- 
lyzed. The duck had lost its feathers and, 
reduced to a skeleton, would still bravely 
eat its oats, but could no longer digest 
them." The duck was 108 years old when 
Rechsteiner, a skilled mechanician, was 
hired to repair it. It was exhibited in Italy 
in 1844 and in London two years later. 
After that it dropped out of sight. Some 
photographs turned up in the early 1950s, 
evidently left by the former curator of 
the Paris Museum of Arts and Crafts. They 
are glass plate negatives that probably date 
from before 1900. The skeleton they reveal, 
together with the appearance of the mecha- 
nism, strongly suggests the wreckage of 
Vaucanson's duck, as they were labelled. 
The plates were said to be from Dresden, 
and if the duck survived World War II, 
one hopes it is in a dry attic. The musicians 
were lost from sight sometime around 1800. 
None of the imitations of Vaucanson's 
automata, including mekaniker Rechsteiner's 
duplicate duck, now survives. These won- 
drous mechanisms are altogether lost. 

Vaucanson himself seems to have pros- 
pered (he was a member of the Academy of 
Science in 1777) and continued inventing. 
In 1741 he devised the system of punched 
cards that controlled looms in the jacquard 
tapestry factory. This is generally considered 
to be the first digital number storage and 
readout system. In 1760 he invented the 



Satisfied with his frugal 
meal, the mechanical 
duck stands up and begins 
to flap his wings and to 
stretch himself while ex- 
pressing his gratitude with 
several contented quacks. 



luly 1978 ra BYTE Publications Inc 57 



Note: 

A complete bibliography 
for this part of "Antique 
Mechanical Computers" will 
appear with "Part 3: Human 
and Machine Action and the 
Torres Chess Automaton" in 
September 1978 BYTE. 



modern metal-cutting lathe, with a shaped 
guideway to prevent chatter and twisting of 
the tool. 

Mechanism of the Automata 

While relatively simple to explain and easy 
to grasp when explained, Vaucanson's 
machines really are very sophisticated in 
performance and embody concepts easily 
100 years ahead of their time. The weight- 
motor is a heavy weight suspended from a 
rope wrapped around a drum windlass, 
which, while slowly falling, drives a gear- 
train (speed controlled by a governor). 
These gears slowly turn a cam-drum, the 
master controller "memory" mechanism, 
one rotation of which equals one perfor- 
mance of the automaton. This drum, per- 
haps the diameter of a small keg and three 
feet long, has on its surface an array of rows 
of studs of some sort, nails or wooden 
knobs. Cam-followers, some sort of spring 
loaded levers, ride on the drum surface, one 
for each row (circle) of studs in the array, 
and each cam-follower is for a moment 
pushed out of place if a stud rotates by to 
push on it. 

There are as many circles of studs on the 
drum as there are functions of the automaton 
to be controlled, and the cam-follower unique 
to that circle of studs does the controlling. 
Thus, one row, say, controls the dilation and 
contraction mechanism of the lips, and 
another row might manage the movements 
of the first finger, left hand, and so on. There 
would be about 1 2 functions to be controlled, 
so about 12 rows or circles of studs are 
on the drum. It is rather like a giant music 
box movement, except that instead of steel 
needles being plucked, cam-followers are 
displaced, and with displacement each fol- 
lower pulls on a flexible cable which is linked 
by its own pulley system to the finger, lip, 
or valve that is unique to it. In some cases, 
like the lip control mechanism, the require- 
ment to produce music is for smooth varia- 
tion from one size to another, so the row of 
studs for that function is replaced by a 
smoothly varying curve, a cam. In other 
cases, the fingering mechanism, a finger 
either does or does not cover a flute hole. 
This is digital control (the word comes from 
counting on the fingers); the former is ana- 
log, meaning that a little movement here 
causes a proportional movement there. 

When it is all put together and regulated 
carefully, the machine will play the flute 
using wind pressures as selected by the 
distributor valve. For the sake of impressive 
appearance, the machine is covered with a 
wooden framework in human shape and is 



clothed, but it would do its job bare. How- 
ever, it would look like a machine and not 
a person. 

The tabor and flageolet player is similar, 
but probably only two levels of wind were 
employed, and the fingering is simpler, 
probably four fingers. 

The duck was essentially a giant version 
of the mechanism that operated the bird 
figures described earlier but with many 
more, and more complex, movements. 
While it is possible that some weight sensitive 
area was built into the pedestal so that the 
duck started to gobble the food only when a 
plate was placed before it, it seems much 
more likely that the operator carefully mem- 
orized the duck's movements (which, of 
course, are identical every time) and returned 
with the plate at just the right moment. 
Otherwise the bird would have been gulping 
down thin air. 

If they still existed, these machines would 
provide an intriguing catalog of early 18th 
century movements, probably including 
some that Vaucanson devised for special 
purposes that would not be rediscovered for 
75 years or more. But, as computers, the 
machines were incredible. Here, 240 years 
ago, was a digital and analog computer 
preprogrammed with perhaps 300 to 500 
bytes of read only memory, each byte 10 
or 12 bits wide. Vaucanson appears to be 
the first person to have seen the need for 
synchronous control of multiple functions 
(how else could you play a flute except by 
regulating breath angle and pressure while 
simultaneously fingering the proper notes?) 
as well as the first who saw \hQ possibility 
of designing mechanisms to effect such con- 
trol. That he used the music box spindle 
approach to his problem is not to his dis- 
credit, for that mechanism was known to 
function reliably over long periods while 
undergoing little wear. His incorporation of 
music box memory devices into an array 
on a single drum (the master controller) 
enabled him to produce some remarkable 
results. He could control a variety of simul- 
taneous, interdependent functions because 
they were all driven by the same "clock." 
This was parallel data processing, in rela- 
tively small chunks, to be sure, but parallel 
beyond doubt. The likes of it were not seen 
again in mechanics until the player piano 
with its paper tape. It is not so very different 
from the way the central nervous system 
deals with data in many parallel channels 
simultaneously. 

But why is this surprising? Jacques de 
Vaucanson was attempting to create life. 
It was his genius to approach the task in 
the manner of living things." 



,1 



58 July 1978 '0 BYTE Publicilions Inc 



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BYTE July 1978 59 



The Z-80 in Parallel 



Bob Loewer 
Micro Diversions Inc 
7900 Westpark Dr 
Suite 308 
McLean VA 22101 



PROCESSOR . 



I 



1 



PROCESSOR, 



Many design engineers have introduced 
various types of parallel processing into 
systems in order to achieve higher through- 
put rates. Almost without exception though, 
these applications have been limited to 
medium and large scale computers due to 
price and complexity. 

In the past two years, microprocessors 
have reached a level of sophistication which 
makes them candidates for parallel processing 
systems. Such systems could conceivably 
offer minicomputer performance at micro- 




P ME MOR V I 32K 



a SHARED MEMORY (52KI 




MEMORY (32K) 



J 



DATA BUS 
I ADDRESS BUS 

I CONTROL BUS 



Figure 1 : The author's parallel Z-80 system. Both processors work indepen- 
dently, each supported by 32 K bytes of programmable memory. The proces- 
sors are linked by 32 K bytes of shared programmable memory. The shared 
memory, addressable by either processor as the upper 32 K, has its own 
address and data buses. Shared memory conflicts are resolved by the arbiter 
circuit shown in figure 2a. 



computer cost. This article is an investiga- 
tion of that idea. 

The Z-80 

The Z-80 microprocessor, manufactured 
by Zilog, is a third generation LSI device 
which offers full software compatibility with 
the 8080 processor. Upgraded features 
provided by the Z-80 include: two sets of 
exchangeable registers, indexing, a full range 
instruction set (including register or memory 
bit operations), eleven addressing modes, a 
nonmaskable interrupt, dynamic memory 
refresh address generation, and an Interrupt 
register to provide a high speed vectored 
interrupt response to any location in 
memory. 

The Z-80's minimum number of control 
bus signals makes it easy to interface in 
multiple processor configurations. 

System Layout 

My design consists largely of two Z-80 
microprocessors (processor X and processor 
Y) operating independently, each supported 
by 32 K bytes of programmable memory 
(see figure 1). The processors are indirectly 
linked by 32 K bytes of common memory, 
making a system total of 96 K bytes. The 
shared memory, addressable by either 
processor as the upper 32 K, has its own 
address and data buses. Data or address 
signals are gated onto their respective bus 
when (1) either processor performs an opera- 
tion involving a read or write against the 
shared memory, or (2) either processor 
attempts an op code fetch from the shared 
memory, or (3) machine instructions com- 
bine (1) and (2). 

Shared memory bus conflicts are resolved 
by the arbiter (see figure 2a). Since the 
processors use opposite phases of the clock, 
requests for bus access can never be initiated 
at exactly the same time. However, depen- 
ding upon the instruction sequences being 
executed, bus request conflicts can occur. 
This problem, summarized in table 3, has 
been carefully examined and is represented 
by figure 3b. It illustrates what is assumed to 



60 



July 19780BYTE Publications Inc 




\ ^ X SELECT 



{^^ Y SELECT 



^l> ^ 



About the Author 






Bob Loewer is an 
employee of the Telenet 
Communications Corpora- 
tion and a graduate stu- 
dent at the University of 
Maryland at College Park. 
He is cofounder of Micro 
Diversions Inc, a company 
Involved with microcom- 
puters and microcomputer 
education. This article de- 
scribes Bob's early re- 
search on parallel micro- 
processor systems. 



\ ^ Y WAIT 



Figure 2a: The shared memory arbiter. This circuit resolves conflicts between the two proces- 
sors if both attempt to gai n simult aneous access to the shared mem ory bus. Fo r example, a 
request from processor X (XMREQ low) will cause IC3a to drive the XSELECT line low and 
will also disable IC3b. Processor Y will be locked out during X's memory reque st. If Y m akes a 
memory request while locked out, the output of IC4a will go low, activating the YWAIT line. 



be the worst possible case of bus conflict; 
both processors simultaneously executing 
shared memory read or write instructions 
from the shared memory. Of course, one 
cannot predict when each processor will 
attempt to access the shared memory, so all 
possible interprocessor state relationships 
have been investigated. 

The basic memory read or write instruc- 
tion has seven "T" cycles (T is defined as 
the duration of one clock period). The T 
states and their functions are: 



M1,T1 
IVI1,T2 
M1,T3 
M1,T4 
M2,T1 
1V12,T2 
M2,T3 



Instruction 
decoding 



Op code fetch 



Memory read or write operation 



The M cycles are machine cycles. Table 3 
shows the seven interprocessor T state align- 
ments: M1,T1 active for one processor when 
states Ml.TI thru M2,T3 for the other are 
active. Figure 3b illustrates an example of 
the processor request signals and signals 
from the conflict arbitration logic. Note that 
after a very short period (maximum of seven 
clock cycles) the arbiter synchronizes and 
thereby provides complete cooperation 
between the two processors' fetch and 



execution cycles by putting one of the 
processors into one or two wait states. 
Further, in the seven possible interprocessor 
T state relationships, there are two in which 
opposing shared memory access request 
signals are synchronized, in which case the 
arbiter does nothing. This means that, 
regardless of the processors' instruction 



Number 


Type 


+ 5 V 


GND 


IC1 


74S04 


14 


7 


IC2 


74S10 


14 


7 


IC3 


74S1 26 


14 


7 


IC4 


74S32 


14 


7 


IC5 


74125 


14 


7 


IC6 


74125 


14 


7 


IC7 


74125 


14 


7 


IC8 


74125 


14 


7 


IC9 


74125 


14 


7 


IC10 


74125 


14 


7 


IC11 


74125 


14 


7 


IC12 


74125 


14 


7 


IC13 


7432 


14 


7 


IC14 


7408 


14 


7 


IC15 


74S157 


16 


8 


IC16 


74S157 


16 


8 


IC17 


74S157 


16 


8 


IC18 


74S157 


16 


8 



Table I: Power wiring 
table for figures 2a and 2b. 



July 1978 ® BYTE Publicalions Inc 61 



SHARED MEMORY DATa BUS 



Figure 2b: Control cir- 
cuitry for tlie siiared 
memory parallel Z-80 
system. The respective 
processor data buses 
and the shared memory 
data bus are shown at 
the top. The shared 
memory address bus 
is at the right. The 
shared memory arbiter 
is shown in the center 
(see figure 2a for a de- 
tailed schematic). This 
circuit works on a first 
come, first served basis 
to resolve all conflicts 
between the two pro- 
cessors. 



<;> 



<i> 



«o^<±> 



<wn |^2>- 



o- 



o 



yi5 O 



0.2 ez A! B3 fl4 B4 



% 






n 






a> 



MD WD MO MD MD MD MD MD 
1 2 3 4 5 6 7 



in> 



t> 



a> 



ICI4 
7408 

E>- 



VXI^ 



Yl Y? yj Y4 se ST 

(CI6 
74SI57 

A2 B2 A3 B3 A4 B4 



2 3 5 6 









M 



te 



13^ 






SHARED 
MEMORY 

ARBITER 



Yl V2 V3 Y4 SE ST 

ICI7 
74S(57 

Al fli A2 82 A3 83 A4 B' 



2 3 5 6 



Yl Y2 V3 Y4 SE ST 

ICI8 
74SI57 

AZ B2 A3 B3 A4 84 



2 3 5 6 



l]hmht)h^Al)h^hhm- AhmhcAc}- mamahh 



<^ 



<^ 



■<? 



-o 






KAIS 
YAI5 

mWr 

X WAIT 
Y WAIT 
XMREQ 
YMREQ 
XRFSH 
VRFSH 






-cp> "« 




SHARED 
1 MEMORY 
/ ADDRESS 



-C!l> "«2 

-(j;> M«a 



PROCESSOR PROCESSOR 



PROCESSOR PROCESSOR 



PROCESSOR PROCESSOR 



PROCESSOR PROCESSOR 



62 luly 1978 © BYTE Publications Inc 



Ml 

-OP CODE FETCH- 



-IVIEMORY READ (OR WRITE)- 



Figure 3a: The basic Z-80 memory read or write cycle. Clock periods are referred to as T cycles 
and the basic operations are referred to as M (for machine) cycles. The first machine cycle of 
any instruction is a fetch cycle (Ml). Subsequent M cycles move data to or from the memory. 



sequences, 86 percent of the time the system 
is at most one wait state away from syn- 
chronization. Thereafter, both processors 
can execute read and write instructions from 
the shared memory at 100 percent processor 
utilization, assuming the instruction syn- 
chronization is not lost. 

Certainly opposing software will not 
consist solely of instructions which offer no 
bus interference. But it is clear that the most 
efficient method of solving the shared mem- 
ory bus conflict problem is the one that will 
achieve short term interprocessor synchroni- 
zation whenever possible. 

Arbitration Logic 

Each processor provides signals to the 
arbiter which identify a valid shared memory 
access request. IC2a and IC2b receive RFSH, 
MREQ, and A15 (the high order address bit 
signal) from their respective processors. 
MREQ indicates that a memory read or 
write operation is underway: either A1 5 line 



going high identifies the shared memory as 
the object of the request; and the RFSH 
lines insure that the dynamic memory refresh 
strobe from one processor will not interfere 
with the shared memory access request of 
the other. 

IC3a and IC3b provide an opposing grant 
or deny shared memory bus access proviso 
that is strictly first come, first served. A 
request from, say, processor X will cause 
IC3a to drive XSELECT low, and coinciden- 
tally disable IC3b. Processor Y will be 
locked out for the length of processor X's 
memory request. Now suppose processor Y 
does make a request for bus access when 
processor X is using the bus. This condition 
will forc e IC4a to its low state, activating the 
YWAIT line. The wait signal will continue 
until processor X concludes its memory 
access. Under no circumstances, however, 
will processor Y be forced into more than 
one wait st ate for this p rocessor X access. 
When XMREQ goes high, XSELECT follows 



Continued on page 174 



Beginning 
Event 


Finishing 
Event 


Stipulation 


Delay Before Occurrence (ns) 


XA15 high 
XRFSH high 
XMREQ low 

XAIBhigh 
XRFSH high 
XMREQ low 

YA15 high 
YRFSH high 
YMREQIow 

YAlShigh 
YRFSH high 
YMREQIow 

XA15 high 
XRFSH high 
XMREQ low 

YA15 high 
YRFSH high 
YMREQIow 






28 


to XSELECT low 


YSELECT high 


to XSELECT low 


YSELECT low 


25 after YSELECT goes high 
28 


to YSELECTlow 


XSELECT high 


to YSELECT low 


XSELECT low 


25 after XSELECT goes high 
53 

53 

22 
22 


to XWAIT low 


YSELECT low 


To YWAIT low 


XSELECT low 


XSELECT high 


to YWAIT high 


YSELECT low 


YSELECThigh 


to YWAIT high 


XSELECT low 



Table 2: Timing considera- 
tions in the arbiter cir- 
cuitry. The arbiter takes a 
finite amount of time for 
its logic circuits to effect 
the changes shown. The 
corresponding delays are 
shown at the right. 



)uly I978©BYTE Publications Inc 63 



Photo 7: Hal Chamberlin's 
home built HAL-4096 
computer system, built in 
1972. This system, which 
is still In service handling 
lO for an IIVIP-16 micro- 
computer system, features 
TTL logic, a 16 bit word 
length, 16 registers, 4 K 
bytes of magnetic core 
memory (a surplus IBIVI 
1620), and priority 
interrupt. 




The First Ten Years of Amateur Computing 



If one could find a 

specific date for the birth 

of personal computing, it 

would be May 5 1966. 



Sol Libes 

President, Amateur Computer Group of New Jersey 

995 Chimney Ridge 

Springfield NJ 07081 



Most people I meet are under the mis- 
taken notion that personal computing 
started only two or three years ago, with the 
introduction of the Altair 8800 by MITS. 
Nothing could be further from the truth. 
In fact, the amateur computing hobby 
was then almost ten years old. 

I therefore decided to write this article 
to set the record straight, give credit to the 
early pioneers in this hobby and shed some 
light on the early history of microprocessors. 

If one could find a specific date for the 
birth of personal computing, it would be 
May 5 1966. For it was on that date that 
Steven B Gray founded the Amateur 
Computer Society and began publishing 
a quarterly called \he ACS Newsletter. 

The newsletter exchanged information 
on where to get surplus computer gear, how 
to build not too complicated circuits, where 
to get integrated circuits, tips, experiences 
and where to get help. By the end of 1966, 
the Society reported that it had over 70 
members. 

1966 also saw the publication of the first 
books on how to build a home computer. 



Typical was We Built Our Own Computers 
by A B Bolt and published by Cambridge 
University Press. 

In January 1968, a survey in the ACS 
Newsletter reported that two amateurs 
had their home built systems up and 
running and that many others were actively 
working on their systems. The survey 
indicated that programmable memory sizes 
ranged from 4 to 8 K with some as high 
as 20 K, all magnetic core of course. Tele- 
types and Flexowriters were popular for 
10. Clock speeds ranged from 500 kHz to 
1 MHz, with the average 500 kHz. Most 
used discrete transistors, and a few reported 
using those new and hard to come by RTL 
integrated circuits. Instruction sets were 
small, ranging from 11 to 34 instructions. 
Word sizes were from four to 32 bits, with 
12 bits the typical number. Registers ranged 
from two to 11, with three most common. 
Most reported that they had been working 
on their machines for about two years. 

The April 1968 issue of Popular Me- 
chanics reported on ECHO IV (Electronic 
Computing Home Operator), a home built 
computer constructed by Jim Sutherland. 
It had four registers, used a 4 bit word, had 
8 K bytes of core memory, 18 instructions 
and a clock speed of 160 kHz. 

In December 1968 Don Tarbell (now 



64 July 1978 © BYTE Publications Inc 




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DOMESTIC SALES 



Circle 372 on inquiry card. 



SALES OUTSIDE CONTINENTAL U.S. 

BYTE July 1978 65 




The first computer kit was 
introduced in 1971. It 
featured 52 TTL inte- 
grated circuits, a 32 by 8 
bit programmable 
memory, and 15 instruc- 
tions for $503. 



Photo 2: The author's TVT-1, designed by Don Lancaster and built in late 
1973. Intended only as a TV typewriter, it was interfaced to a modem and 
used with an IBM timesharing system. 



known for his high speed tape cassette 
interface) reported on his home built com- 
puter in the ACS Newsletter. It had a 4 bit 
word size, four registers, 10 kHz clock and 
was constructed using RTL integrated 
circuit logic. He used a Teletype for 10. 

In 1967, Dave Digby ran an ad in CQ 
magazine offering a computer kit. It was 
advertised as featuring RTL logic, four 
registers, a 512 to 1024 byte delay line 
memory, and serial input and output. The 
price was $1000. As far as I know, he 
never delivered any units. 

Most early builders constructed copies 
of the Digital Equipment Corporation's 
PDP-8 minicomputer with their own modifi- 
cations. In the surplus area, 1000 Minute- 
men I missile guidance processors became 
available in 1971. 

1971 also saw the introduction of the 
first computer kit. It was part of the 
National Radio Institute's course on com- 
puter electronics. It used 52 TTL integrated 
circuits, had a 32 by 8 bit integrated circuit 
memory, 15 instructions and an operator's 
panel, and it sold for $503. Louis E Frenzel, 
then of NRI and now at Heathkit, was the 
designer. 

In late 1971, the Kenback Corporation 



The Kenback-1 computer 
featured a 1 K byte MOS 
shift register memory 
made by a small, young 
manufacturer called Intel. 



introduced the Kenback-1 computer for 
$750. It was intended primarily for educa- 
tional use. It had a 1 K byte MOS shift 
register memory made by a small, young 
integrated circuit manufacturer called 
Intel. It also had three registers, an 8 bit 
word size, 65 instructions, operator's panel, 
and an audio cassette for program storage. 

The December 1971 issue oi Computers 
and Automation described five home built 
computer systems. And by the end of the 
year 1971, there were reported to be 195 
members in the Amateur Computer Society. 

In 1972 things continued to pick up. In 
June Don Tarbell reported that he had 
written an editor program for his new home 
built system and was working on an as- 
sembler program. His system used an 8 bit 
word, 16 registers, and 4 K bytes of core 
memory. 

Early 1972 saw the introduction of the 
8008 microprocessor, by Intel, the opening 
of a number of used computer equipment 
stores, large price drops in TTL logic and the 
availability of the 1101 programmable 
memory at low cost. All of this proved to be 
a tremendous stimulus for amateur com- 
puter experimenters. 

In the September 1972 issue of the ACS 
Newsletter Hal Chamberlin reported on his 
home built HAL-4096. This 16 bit machine 
utilized surplus IBM 1620 core memories. 
Hal furnished a complete set of construction 
plans for $2. The system had 16 registers, 
priority interrupt, Selectric and paper 
tape 10, and many other very advanced 
features. 

The September 14 1972 issue of Elec- 
tronic Design carried an article on how to 
build a circuit which would display 1024 
ASCII characters on a TV set. 

In 1973 amateur computing advanced 
in several areas. In May, the EPD company 
advertised the System One computer kit 
for $695. It had 1 K bytes of memory 
with expansion to 8 K and contained 82 
integrated circuits. It had 57 instructions 
encoded in a diode matrix read only 
memory. 

The September 1973 issue of Radio 
Electronics published Don Lancaster's plans 
for the construction of the TVT-1 . Although 
intended as a TV typewriter, many enter- 
prising experimenters interfaced it to 
modems and home built computers. 

In late 1973, the Sceibi Computer 
Consulting Company introduced the 
first computer kit using a microprocessor. 
The kit was called the Scelbi-8H and it sold 
for $565. It used the Intel 8008 and had 



66 luly 1978 © BYTE Publications Inc 



see TURNOFF RELRV 6 : DELflV 
300: REM STOP ARM.. WRIT 

sense inputs 

liiiwmiihimtiiiiiiitiifc 



210 



TURf-40N LITE 4 : REM 



Expansion bus 

Socl(ets for 
up to 16l( of 
on-board RAM 




8 user definable 
indicator lites 



ZIBLTM Lite port 

in PROIM displays an 

8-bltword 



Programming slots 

for 2 TMS 2716s; stores 

user's programs 



4 3/4-amp 
reed relays 



4 general purpose 
relays, 5 amp at 115 VAC 



Dynabyte*s new Basic Controller: Check out 
its capabilities and imagine your applications 



The Basic Controller^'^ is a powerful, 
versatile and easy to use single board 
microcomputer system designed for 
control applications. 

It is heavily into control I/O: relays, 
flags and sense inputs. What makes 
controlling these l/Os (and the external 
devices they control) so easy is our ZIBL^"^ 
(Z-80 Industrial Basic Language). It is a 
superset of NIBL, National Semiconduc- 
tor's control BASIC, and was written by us 
specifically for control applications. 

We've divided the control world into six 
categories: sense inputs, flag outputs, lites, 
relays, A/Ds and D/As. ZIBL implements 
64 channels of each in such a way that you 
need not know anything more about them 
than their names. 

In ZIBL it is valid to say: 

1 00 IF TIME = 053010 AND SENSE 
(18) = OTURNON RELAYS 
Simple, isn't it! 

Some but not all of the Basic 
Controller's mouth watering features 

Circle 1 10 on inquiry card. 



include: 

• File structures that allow multiple 
programs written in ZIBL to reside 
concurrently in RAM. Each program may 
be individually LOADed, RENAMEd, or 
RUN. Any program may access another 
program as though it were a subroutine, 
while still retaining its own line numbers 
and variables. 

• Complete communication versatility. 
LISTing, PRINTing and INPUTing may be 
done to or from any serial or parallel I/O 
channel or the self-contained CRT I/O. 

• Single key SAVE or LOAD to and 
from cassette. 

• Single key SAVE to EPROM. No worry 
about PROM addressing or programming 
routines, it is handled by ZIBL — 
automatically — even if there are other 
programs already in PROM. 

• ZIBL in ROM: TURNON, TORNOFF 
DEUW, TIME, REM, IF THEN, DO GNTIL, 
GOTO, GOSGB, @(exp), TRACE MODE, 
UNK, READ, DATA, DIR, RND(x,y), strings 



triple precision integer arithmetic, plus the 
usual statements. 

• Onboard: Z-80 MPU, 32 flags, 32 
sense, 8 relays, 8 lites, 2 serial, 1 parallel, 
cassette I/O, 64x16 video, keyboard port, 
two 2716 sockets with programming 
capability, up to 16k on-board RAM, up to 
48k off-board RAM, real time clock, 
vectored interrupts, Lite Port on board, a 
kitchen sink, and an Expansion Bus. 

$750 assembled, tested, warranted 1 
year. You add power supply, keyboard and 
monitor. Available now — see your 
computer retailer. 

1 005 ElwellCt, Palo Alto, CA 94303 (415)965-1010 




BYTE luly 1978 67 



1 K bytes of integrated circuit program- 
mable memory. It was expandable to 16 K 
bytes of programmable memory ($2760) 
and had options such as cassette 10, ASCII 
keyboard input, oscilloscope output and 
serial 10. 

In 1973, Digital Equipment Corporation 
offered the PDP-8A with 1 K words of 1 2 
bit programmable memory for $875. Also 
in 1973, a small publishing house catering 
to computer and digital electronics hobby- 
ists began publishing with a book on wire 
wrap construction techniques. It was called 
M P Publishing Company and was a part 
time activity of Carl Helmers (who later 
began a monthly called Experimenters' 
Computer System which after five issues 
was transformed into BYTE in 1975). 

1974 marked a year of substantial in- 
crease in amateur computing. In July, 
Radio-Electronics magazine carried a con- 
struction article by Jonathan Titus on 
building the Mark-S processor, which 
used the Intel 8008 microprocessor. It is 
estimated that over 500 of these units 
were built by avid experimenters. 

In October, Southwest Technical Pro- 
ducts Company (SwTPC) introduced the 
TVT-II kit for $180 and an ASCII key- 
board kit for $40. 

In September, Hal Singer started the 
IVIicro-8 Newsletter to exchange information 




Photo 3: The author's Mark-8 processor, built in late 1974. Designed by 
Jonathan Titus, it uses the Intel 8008 microprocessor and has I K bytes of 
programmable memory. 



among hundreds of experimenters who were 
building the Mark-8 unit. 

In November 1974, Hal Chamberlin and 
some associates began another very popular 
but short-lived magazine called The Com- 
puter Hobbyist. 

1975 was the year that personal com- 
puting exploded. It began, in January, when 
Popular Electronics carried an article on the 
Altair 8800 microcomputer by MITS. First 
deliveries were in April 1975. The kit sold 
for $375 and included 1 K bytes of pro- 
grammable memory, but no 10. MITS claims 
that by the end of 1976 they had sold over 
10,000 Altair 8800s (80% to hobbyists). 

In April, the first computer club held 
its meeting. Started by Bob Reiling and 
Gordon French, and calling itself The 
Homebrew Computer Club, it met in Menio 
Park CA. One month later the Amateur 
Computer Group of New Jersey was formed. 

In the fall of 1975, MITS released its 
4 K and 8 K BASIC interpreters, SwTPC 
introduced their 6800 based microcomputer, 
and the first decade of amateur computing 
was complete. Since then, the field as we 
know it today has rapidly matured and 
expanded. 

Some Microprocessor History 

Intel Corporation must be credited with 
developing the microprocessor, the single 
chip integrated circuit which performs the 
basic functions of a central processing unit. 

In 1969, a Japanese company, Busicom, 
contracted with Intel to develop a chip set 
for a printer-calculator. It used a 4 bit data 
bus and consisted of four integrated circuits 
in a set: a processor, read only memory with 
10, programmable memory with lO, and a 
shift register type memory. Busicom per- 
mitted Intel to market the chip set for 
noncalculator applications, and the first 
generation of microprocessors was born. 

The processor chip was designated the 
4004, and it sold for $200. It came in an 
18 pin dual in line package (DIP) and would 
interface only with the other chips in the 
family. Programs had to be stored in the 
erasable read only memory. Data and 
address information was multiplexed 
on the 4 bit bus. Since program could 
only be executed out of read only memory, 
and since progammable memory was used 
only to store data, debugging software 
proved to be difficult. Further, a great 
deal of support logic was required. 

At nearly the same time, Datapoint, 
a manufacturer of intelligent terminals, 
contracted with Intel and Texas Instru- 
ments to produce a true processor on a 



68 July 1978 @ BYTE Publlcitiom Inc 



An IMFO 2000 DISK SYSTEM 

gives you a lot less 
than you expected: 



Less Cost 



Less Hassle 



The DISCOMEM Controller board costs us less to 
manufacture. So your complete INFO 2000 Disk 
System costs you less - at least $400 less than com- 
perable disk systems. 



Less Hardware 

Only three S-100 boards are needed to create a com- 
plete, high-performance disk-based microcomputer 
system-the DISCOMEM Controller Board, a 32K 
memory board, and any 8080, 8085 or Z80 CPU 
board. You don't need extra interface or EPROM 
boards since DISCOMEM contains 2 serial ports, 3 
parallel ports and provision for 7K of EPROM and IK 
of RAM. 



LessTime 

The INFO 2000 Disk Sys- 
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seek times are up to 8 
times faster than with 
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disk copy and verification 
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Formatting and verifying a 
new diskette takes less 
than half a minute. Reload- 
ing CP/M* from diskette 
takes a fraction of a se- 
cond. 

Less Space 

The system is remarkably 
compact, requiring only 
1/2 to 1/3 the space taken 
by other 2-drive disk sys- 
tems. 



The INFO 2000 Disk System eliminates the "I/O configuration 
blues" by incorporating all necessary interface ports. A CP/M 
Loader and all I/O drivers are contained in EPROM so there 
is no need for special software customization. Just plug 
the system into your S-100 microcomputer and 
begin immediate operation using the CP/M 
disk operating system. The INFO 2000 
Disk System is supported by the 
most extensive library of software 
available, including 3 different 
BASICS, 2 ANSI FORTRAN IVs, 
several assemblers, text editors, de- 
bugging tools, utilities and numerous 
applications packages. 



Less Errors 

This disk system uses full size 8" 
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ffliuuuiiuiiiUttiiii 



It all adds up to more capability for your money. 

The complete INFO 2000 Disk System comes completely assembled and tested. It includes dual 

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Dealer inquiries welcomed. •Cp/M is a registered trademark of Digital Research. 



Circle 178 on inquiry card. 



BYTE |ulv 1978 



69 



.m^' 




t mn ^;':. ,N.^ ^^. 



• A' ■'-/ 



■i-«ff*\- 









.^ ^ / 






/'//o^o 4; /?o^er Amidon's 
4 bit processor, built in 
1972 and fondly referred 
to as the "Spider. " It 
was built with TTL logic 
and used to control an 
amateur radio (R TTY). 
The Spider was featured 
on the cover of April 1977 
BYTE. 



chip. Intel succeeded in doing this. Un- 
fortunately, the device proved to be too 
slov/ for Datapoint's use. Intel decided, 
therefore, in 1971, to market the device for 
$200 and call it the 8008. It marked the 
first generation of "true" microprocessor 
integrated circuits. 

The 8008 used an 8 bit data word with 
a more powerful instruction set than the 
4004, but it still had many of the disadvan- 
tages of the 4004. It required considerable 
support logic. The 8008 however was a 
more general purpose device. For example, 
it contained a set of logical operations that 
the 4004 did not have. Its instruction set 
was similar to a minicomputer's, and it 
could directly address 16 K bytes of pro- 
grammable memory. It even had interrupt 
capability. 

At the same time, Intel introduced the 
1101, a 256 by 1 bit programmable 
memory (which enabled the experimenter 
to build a 1 K by 8 bit memory with only 
32 integrated circuits!), and the 1702 
256 by 8 bit EROM. With the 8008, 1101 
and 1702 integrated circuits, general purpose 
computers could now be built. 

In 1972 several other manufacturers 
recognized this emerging market. Most 
notable was National Semiconductor who 
introduced the IMP-16, a chip set which 
may have been a little ahead of its time. 
It was a bit slice system of variable word 



length and user definable instruction set. 
It later developed into the third generation 
Pace microprocessor. 

In late 1973, Intel introduced the 8080 
processor, and, soon after. Motorola intro- 
duced the 6800. The 8080 has become the 
de facto industry standard, used in more 
applications than any other processor. The 
8080 is basically an enhancement of the 
8008. It came in a 40 pin dual in line 
package and could directly address 64 K 
bytes of programmable memory and read 
only memory. It had a true bidirectional 
data bus and an expanded instruction set. 
However, it still required an external clock 
and multiple power supplies. The 6800 
on the other hand required only one TTL 
compatible power supply, had simpler 
control circuitry, and an instruction set 
more compatible with larger computers. 

1975 and 1976 saw the introduction 
of enhanced third generation micro- 
processors. The Zilog Z-80, an enhanced 
8080, featured a larger instruction set, 
more registers, on chip clock, and more. 
The 6502, from MOS Technology, was an 
enhancement of the 6800. The Texas 
Instruments TMS9900 and TMS9980 
became the first widely available single 
chip 16 bit microprocessors. 

1977 marked the introduction of the 
fourth generation of microprocessors. In 
fact, these devices now could be called 



70 luly 1978 © BYTE Publicitions Inc 



microcomputers in a single integrated 
circuit. Tliese new devices include the 
complete microprocessor, read only 
memory, programmable memory, and 
10 circuitry on one chip. A minimum of 
support logic is required. 

The future promises an increase in word 
size, functions, speed and memory capacity. 
(It looks like the single chip processor 
that runs BASIC may soon be a reality.) 
The next ten years in microprocessors and 
personal computing should be even more 
amazing than the past decade." 



Photo 5: The Scelbi-SH processor. This was 
the first kit to utiiize a microprocessor. It 
employed an Intel 8008 processor and was 
introduced in late 1973; design work began 
on the unit in August 1972. The prototype 
featured an oscilloscope display and audio 
tape unit. Sceibi has since discontinued their 
hardware line to concentrate on software 
and applications publications. The last 
Scelbi-8H was sold in December 1974. 




TURTLES 



Small home robots 
controllable by your computer. 

Attachable to any computer via parallel interface (not included) 

Terrapin^" Turtles can: 

• 'walk' (on 2" radius wheels) 

• 'talk' (via 2-tone speaker) 

• 'blink' (with lights as eyes) 

• 'draw' (with solenoid-controlled pen) 

• 'feel' (using S'/?" radius dome as touch sensor) 

Use your Turtle to map rooms, solve mazes, dance, ex- 
plore Artificial Intelligence, teach geometry or 
programming. 

A unique peripheral to keep you "in touch" with your 
computer. 

Limited delivery from stock • Brochures available 




Kit $300 Assembled $500 



Terrapin, Inc. 



S-100 Interface $40 Shipping $5 
Mass. residents add 5% sales tax 



33 Edinborough Street, 6th Floor 
Boston, MA 02111 
(617) 482-1033 



Circle 374 on inquiry card. 



July 197g@BYTE Publications Inc 71 



f5V 



GO [I> 

dirO 




560ii 

(TYPICAL FOR 6) 



Figure 1: Schematic diagram for t/ie motor driver. The 7400, Id, has +5 V 
connected to pin 14 and pin 7 is connected to ground. 



Controlling DC Motors 



Robert L Walton 
5616 Houston Rd 
Eaton Rapids Ml 48827 



About the Author; 



Robert Walton is a 
process computer engineer 
employed by Consumers 
Power Company. He has 
designed and homebrewed 
an 8008 based system with 
9 K of memory, Kansas 
City audio tape interface, 
ASCII keyboard, 128 by 
128 dot graphic video 
interface, and a front 
panel which allows exam- 
ination and modification 
of contents in memory 
during program execution. 
More recently he has been 
experimenting with a 
KIM-1. 



This article wilt explain one inexpensive 
way to control the position of asnnall 1.5 V 
to 3 V hobby DC motor to within a quarter 
turn out of a total range of 16,384 turns. 
Various types of mechanical apparatus may 
be attached to this shaft for accurate posi- 
tioning. The feedback portion of this circuit 
may be used alone for position sensing of 
shafts which reverse direction during opera- 
tion. Modifications to obtain resolution 
better than a quarter turn and to drive 
higher powered DC motors will be discussed. 

The impetus for developing this circuit 
came while estimating the cost and com- 
plexity of implementing the circuit shown 
by Leon Sweer, Thomas Dwyer and Margot 
Critchfield in the article "Controlling Small 
DC Motors with Analog Signals" (August 
1977 BYTE, page 18). My lack of a digital 
to analog converter, the apparently high 
power dissipation in the power op amp, and 
the mechanical complexity of the feedback 
potentiometer gear reduction were all 
negative factors. An "all digital" scheme was 
devised to overcome these problems. 



The motor driver circuit is shown in 
figure 1. The circuit is simplified consider- 
ably by the presence of only three modes of 
operation: full forward, full reverse, and 
completely stopped. All transistors are in 
cutoff or sat uration at all times. The signals 
labeled FOR and REV are at a high l evel, + 5 
V, while the motor is stopped. When FOR is 
brought low, Q1, Q4, and Q6 become 
saturated, or "turned on." This effectively 
connects motor pin 1 to+5 V and motor 
pin 2 to ground. When REV is brought low, 
Q2, Q3, and Q5 conduct, connecting motor 
pin 1 to ground and motor pin 2 to -i-5 V. 

Note that FOR and REV must never be 
grounded simultaneously; if this situation 
occurs, heavy current will flow through Q1, 
Q2, Q3, and Q4, potentially damaging the 
devices. To eliminate the possibility of this 
happening due to a programming bug while 
the moto r dri ve is connected to a computer, 
the FOR and REV signals have been modified 
to GO and DIR signals by the gate logic of 
ICl. The motor will be stopped as long as 
the GO signal is low. It will run forward 



72 luly 1978 e-BYTE Publicilions Inc 



p= ^^ \L^^^ M 'f^^ ^um(^iim ^ 




MODEL CC-8 

$185.00 (4800 Baud) 

$195.00 (9600 Baud and 220V/50 Hz) 



9600 BAUD CASSETTE RECORDER 

An ASYNCHRONOUS NRZ type Recorder with remote motor start/stop. Error rate 
108 at 4800 BAUD. Can be used from 110 to 9600 BAUD into a UART - no clocking 
required. This is not an audio recorder. It takes RS232 or TTL signals from the terminal or 
computer and gives back the same signals. No audio interface is used. Motor start/stop is 
manual or through TTL or RS232 signals. 

Tape speeds are 1.6" / 3.0" and 6.0" per second. 110 volt, 60 Hz, 5 v/atts. (220 Volts on 
special order). Can use high quality audio cassettes (Philips Type) or certified data cassettes. 
Can be used in remote locations from a 12 Volt battery. 

Recommended for DATA LOGGING, WORD PROCESSING, COMPUTER PROGRAM 
RELOADING and DATA STORAGE. Manual control except for motor start/stop. 6800, 
8080 or Z80 software for file or record searching available on request with order. Used by 
major computer manufacturers. Bell Telephone and U.S. Government for program reloading 
and field servicing. 



AVAILABILITY - Off the shelf. 



PROVIDES MONITOR AND TAPE SOFTWARE in ROM. TERMINAL and TAPE PORTS 
on SAME BOARD. CONTROLS ONE or TWO TAPE UNITS (CC-8 or 3M3B). 

This is a complete 8080, 8085, or Z80 system controller. It provides the terminal I/O 
(RS232, 20 mA or TTL) and the data cartridge I/O, plus the motor controlling parallel I/O 
latches. Two kilobytes of on board ROM provide turn on and go control of your Altair or 
IMSAI. NO MORE BOOTSTRAPPING. Loads and Dumps memory in hex on the terminal, 
formats tape cartridge files, has word processing and paper tape routines. Best of all, it has 
the search routines to locate files and records by means of six, five, and four letter strings. 
Just type in the file name and the recorder and software do the rest. Can be used in the 
BiSync (IBM), BiPhase (Phase encoded) or NRZ modes with suitable recorders, interfaces 
and software. 

This is Revision 8 of this controller. This version features 2708 type EPROM's so that 
you can write your own software or relocate it as desired. One 2708 preprogrammed is 
supplied with the board. A socket is available for the second ROM allowing up to a full 2K 
of monitor programs. 

Fits all SI 00 bus computers using 8080 or Z80 MPU's. Requires 2 MHz clock from bus. 
Cannot be used with audio cassettes without an interface. Cassette or cartridge inputs are 
TTL or RS232 level. 

AVAILABILITY - Off the shelf. 




2SIO (R) CONTROLLER 
$190.00, Tested & Assmb. 



itiiiiii"*'"'"'* 




6800 CONTROLLER for SWTP 
$190.00, Tested & Assmb. 



PROVIDES MONITOR AND TAPE SOFTWARE in EPROM. EXPANDS MIKBUG with IK 
of ADDITIONAL ROM PROGRAM 

This is a complete tape controller for the SWTP 6800 system. Has 3K of EPROM space 
for your own programs. A 1 K ROM (2708) is provided with all tape and monitor functions. 
The ROM program is identical to our extensive 8080 ROM program. 

Has one ACIA for one or two tape drives, one UART for an additional Serial port and a 
4 bit parallel port for motor control. Will control one or two CC-8 or 3M3B drives with the 
software provided. Can be used with other tape drives controllable with 4 TTL bits if 
appropriate software changes are made. 

Extra serial port is provided for your use with a second terminal or printer (RS232, TTL 
or 20 ma). 

The ROM program supplements the MIKbug program and is entered automatically on 
reset. SWTbug compatible ROM is also available. 

AVAILABILITY - Off the shelf. 



Z 80 BOARD for SWTP COMPUTER 

Now you can use the 8080/Z80 software programs in your SWTP 6800 machine. Re- 
places your MPU board with a Z80 and ROM so that you are up and running with your 
present SWTP memory and MPS card. 1 K ROM on board replaces MIKBUG. 

AVAILABILITY - Off the shelf. 




_$190.00, Tested & Assmb. 



For U.P.S. delivery, add $3.00. Overseas and air shipments charges collect, N.J. Residents add 5% Sales Tax. WRITE or CALL for further 
information. Phone Orders on Master Charge and BankAmericard accepted. 

Naticnal Multiplex Cerpcraticn 

j 3474 Rand Avenue, South Plainfield NJ 07080 Box 288 Phone (201) 561-3600 TWX 710-997-9530 c^^,^^. 



Circle 275 on inquiry card. 



BYTE July 1978 73 




Figure 2: Opaque disk to 
be attaclied to motor 
stiaft. Two gaps are cut 
so ttie disl^ will be rota- 
tionaiiy balanced. 



when GO and DIR are high, and reverse 
when GO is high and DIR is low. The DIR 
signal may be reversed with GO remaining 
high without damage. This reversal may 
occur as often as desired, even many times 
per second, without electronic damage. 
Diodes D1, D2, D3 and D4 are used to 
suppress switching transients from the 
motor. 

Higher powered motors or higher voltage 
motors may be accommodated by using 
7426 open collector gates in place of the 
7400 gates or by using additional transistor 
driver stages, as appropriate. 

Position Feedback 

Determining how many times a shaft has 

turned in one direction is simple. Attach an 
opaque disk with periodic gaps in it to the 
shaft as shown in figure 2. Shine a beam of 
light on one side of the disk and place a 
phototransistor on the other side. Apply the 




TOP VIEW 



MOTOR 



SlOe VIEW 



Figure 3: Placement of phototransistors A and B. Thie ptiototransistors 
should be within an eighth of an inch of the disk. The disk should be opaque 
and painted flat black. The 60° gap size and 30° placement of the photo- 
transistors will provide a steady count once every 90 of rotation. 



DARK fl 
LIGHT 



DARK B 



DARK A 
LIGHT 



r 



4a COUNTERCLOCKWISE ROTATION 



r 



4t: CLOCKWISE ROTATION 30» ROTATION 

Figure 4: Phototransistor timing diagram. Note that the counter must count 
up when a dark to light transition occurs on A and B is dark, or when a light 
to dark transition occurs on B and A is dark. The counter must count down 
when a dark to light transition occurs on B and A is dark or when a light to 
dark transition occurs on A and B is dark. This assumes that a counterclock- 
wise rotation causes an increase in count. 



output of the phototransistor to a Schmitt 
trigger and count the high to low transitions. 
Note that it is not possible to determine 
the direction the shaft is rotating by observ- 
ing the electrical signals generated. 

By adding another phototransistor, it is 
possible to determine the direction the shaft 
is turning. The two phototransistors, identi- 
fied as A and B, must be arranged as shown 
in figure 3. The direction of rotation can be 
determined by observing which photo- 
transistor is the first one on when the gap 
is encountered as shown in figure 4. The 
direction can also be determined by observ- 
ing which phototransistor is the last one 
off. It is really necessary to use both of these 
transitions in order to avoid miscounting 
when the oscillating situation explained in 
the caption of figure 5 is encountered. 

The circuit to detect and register the 
shaft turns is shown in figure 6. This circuit 
functions by propagation delay. Signals A 
and B are high when their respective photo- 
transistors are on. Signals AD and BD are 
signals A and B, respectively, delayed by 
passing through four inverters. Similar 
terminology applies to A-hB and (A+B)D. 
These signals are then "anded" and "ored" 
together to make up and down counting 
signals for the four cascaded counters. 

The four counters provide 16 bits of 
position information, or one part in 65,536. 
In the unlikely event that additional preci- 
sion is required, more counters may be 
added. Note that the circuit generates four 
counts per revolution. If more counts per 
revolution are required, additional narrower 
gaps may be cut in the opaque disk and the 
phototransistors may be placed closer 
together. 

Construction 

The opaque disk may be made from a 
sandwich of two index cards and aluminum 
foil glued together. The disk may then be 
drilled to fit the motor shaft and fastened 
with a drop of epoxy. If the motor shaft is 
mounted vertically with the disk up, the 
phototransistor may be mounted beneath 
the disk. An incandescent desk lamp may be 
used to illuminate the disk. The photo- 
transistors may have to be adjusted a little 
to get the unit functioning. Be sure the 
collector of each phototransistor reads over 
4 V when dark and under 0.5 V when 
illuminated. Be sure this is true all the way 
around the disk. Note: you will not be able 
to see the up and down counter inputs or 
the outputs of the four "and" gates on any 
but the very fastest oscilloscopes. 

To test the circuit, wire the GO motor 
input high and wire pin 7 of IC7 (figure 6) 



74 )ulv 1978©BYTE Publications Inc 



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P39299 



Circle 219 on inquiry card. 



BYTE luly 1978 75 




Photo J: A breadboard of the motor controller. The photocells may be seen In front of the 
motor. • . 



to the motor DIR input. Tie tine LOAD 
input (figure 6) to +5 V. The motor should 
seel< one end of one of the gaps and 
"chatter" there. The rate of chatter may be 
anywhere from five to 100 times per second. 
The angle the disk turns during this chatter 
should be only a few degrees. Experiment 
with the lighting to obtain the fastest chatter 
rate. Passing your hand in front of the lamp 
will cause the motor to run away. When 
your hand is removed, the shaft will again 
seek a position. 

Use 

It is wise to have a mechanical arrange- 
ment using a slipclutch or a similar device to 



prevent mechanical or electrical damage if 
the motor runs away. Such an accident 
could result from a program problem or a 
burnt out light source. Such an arrangement 
also provides the facility for automatically 
zeroing the position when power is first 
applied to the circuit. The motor is driven in 
one direction long enough to ensure that the 
slipclutch is slipping, and then the LOAD 
line is momentarily lowered to load the 
counters with the known position. The 
counters will then contain the correct ab- 
solute position until power is turned off or 
the slipclutch operates again. 

To set the motor to a specific position, 
perform the program in listing 1 (flowchart 



POSITION OF A -,, 




POSITION OF A--_ 



POSITION OF B--' 




nttBK A 




























LIGHT 
nABK- p 





















































Figure 5: Reason for decoding trailing edge of signals. A 30° oscillation of the disk between the 
positions shown will create the above waveform. If the trailing edge was not decoded, the 
counter would be decremented once for each oscillation and lose track of the correct position. 



76 )uly 1978 ©BYTE Publicaliom Inc 



the electric pencil II 

^^ e 1Q78 Mirhafil ?ihraver 



TM 



"Hie Electric Pencil II is a Character Oriented 
Word Processing System. This means that text is 
entered as a string of continuous characters and 
is manipulated as such. This allows the user 
enormous freedom and ease in the movement and 
handling of text. Since line endings are never 
delineated, any number of characters, words, 
lines or paragraphs may be inserted or deleted 
anywhere in the text. The entirety of the text 
shifts and opens up or closes as needed in full 
view of the user. The typing of carriage returns 
as well as word hyphenation is not required 
since lines of text are formatted automatically. 



1978 Michael Shrayer 

As text is typed in and the end of a screen 
line is reached, a partially completed word is 
shifted to the beginning of the following line. 
Whenever text is inserted or deleted, existing 
text is pushed down or pulled up in a wrap 
around fashion. Everything appears on the video 
display screen as it occurs which eliminates any 
guesswork. Text may be reviewed at will by 
variable speed scrolling both in the forward and 
reverse directions. By using the search or the 
search and replace function, any string of 
characters may be located and/or replaced with 
any other string of characters as desired. 



When text is printed. The Electric Pencil II automatically inserts carriage returns where they 
are needed. Numerous combinations of line length, page length, line spacing and page spacing allow 
for any form to be handled. Character spacing, BOLD PACE, multicolumn as well as bidirectional 
printing are included in the Diablo versions. Right justification gives right-hand margins that are 
even. Pages may be numbered as well as titled. This entire page (excepting the large titles and 
logo) was printed by the Diablo version of The Electric Pencil II in one pass. 



NowonCP/M 

You've probably seen 
The Electric Pencil in 

action by now. It's the 
most powerful 8080/Z80 
character oriented word 
processor on the market 
today. Michael Shrayer is 
now proud to present the 
new Electric Pencil II. 



NEW FEATURES : !! 

Supports Four Disk Drives 
Disk Storage and Retrieva 
Printing !!! Print Value 
Bidirectional Multispeed 
Print Value Scoreboard 
Cassette Backup Capabili 
Control !!! Non-Print 
Indentation !!! Centering 



! CP/M Compatible 1!! Disk Operating System 
! ! ! Simple File Management ! ! ! Quick and Easy 

1 !!! Dynamic Print Formatting !!! Multicolumn 
Chaining !!! Page-at-a-time Scrolling !!! New 
Scrolling Controls 1!! New Subsystem with 

! ! ! Automatic Word and Record Number Tally ! ! ! 

ty ! ! ! Full Margin Control !!! End-of-Page 

ing Text Commenting ! ! ! Line and Paragraph 
! ! ! Underlining ! ! ! BOLD FACE ! ! ! 



WIDE SCREEN VIDEO!!! 

Available to Imsai VIO video users for a huge 80x24 character screen !! 



HAVE WE GOT A VERSION FOR YOU ? 

The Electric Pencil II operates with any 8080/Z80 based microcomputer that supports a CP/M disk 
system and uses a Imsai VIO, Processor Technology VDM-1, Polymorphic VTI, Solid State Music VB-IB, 
Vector Graphic Flashwriter or any similar memory mapped video interface. Specify when using CP/M 
that has been modified for Micropolis or North Star disk systems as follows: For North Star add 
suffix A to version number, for Micropolis add suffix B to version number, e.g. SS-IIA, DV-IIB. 



Vers. 


Video 


Printer 
TTY or similar 


Price 


SS-II 


SOL 


$225. 


SP-II 


VTI 


TTY or 


similar 


$225. 


SV-II 


VDM 


TTY or 


similar 


$225. 


SI-II 


VIO 


TTY or 


similar 


$250. 


DS-II 


SOL 


Diablo 


1610/20 


$275. 


DP-II 


VTI 


Diablo 


1610/20 


$275. 


DV-II 


VDM 


Diablo 


1610/20 


$275. 


DI-II 


VIO 


Diablo 


1610/20 


$300. 



ss 



MICHAEL SHRAYER SOFTWARE 

1253 Vista Superba Drive 

GLendaLe, CA 91205 

(213) 956-1593 



The Electric Pencil I is still available for non CP/M users: 



coming 
attractions 

Sort & Merge Utility !!! 

The NEC printer package !!! 

The HELIOS Electric Pencil ! ! ! 

Pencil to CP/M file conversion ! ! ! 

CP/M to Pencil file conversion ! ! ! 



Vers. 


Video 


Printer 


Cassette 


Disk Drive 


Price 


SS 


SOL 


TTY or 


similar 


CUTS 





$ioo. 


SP 


VTI 


TTY or 


similar 


Tarbell 





$ioo. 


sv 


VDM 


TTY or 


similar 


Tarbell 





$100. 


SSN 


SOL 


TTY or 


similar 


CUTS 


North Star 


$125. 


SPN 


VTI 


TTY or 


similar 


Tarbell 


North Star 


$125. 


SVN 


VDM 


TTY or 


similar 


Tarbell 


North Star 


$125. 


DS 


SOL 


Diablo 


1610/20 


CUTS 





$150. 


DP 


VTI 


Diablo 


1610/20 


Tarbell 





$150. 


DV 


VDM 


Diablo 


1610/20 


Tarbell 





$150. 


DSN 


SOL 


Diablo 


1610/20 


CUTS 


North Star 


$175. 


DPN 


VTI 


Diablo 


1610/20 


Tarbell 


North Star 


$175. 


DVN 


VDM 


Diablo 


1610/20 


Tarbell 


North Star 


$175. 



Demand a demo Srom your dealer I 



Circle 316 on inquiry card. 



BYTE jury 1978 77 



in figure 7) at least twenty times per second. 
On an 8 bit machine, reading a 16 bit real 
time quantity poses a problem. If one byte 
is read and then the other, there is a real 
possibility that the 16 bit input may have 
changed between the two operations. 
Therefore the position is read twice and 
checked for agreement before proceeding. 
With a 16 bit machine, only a single input 
operation need be performed. 



The motor will race at top speed toward 
the desired setting. When it goes past the 
setting, it will turn around and race back, 
again overshooting. After a couple of quick 
oscillations, the desired position will have 
been reached and the motor will shut off. 
A better algorithm could be devised by 
estimating the speed of the motor and 
anticipating the overshoot, causing the 
motor to approach zero speed very close to 



Figure 6: Schematic dia- 
gram for the encoder cir- 
cuit. The data input lines 
should be wired to the 
state corresponding to the 
desired initial position of 
the motor. The dotted in 
capacitors may be required 
to obtain sufficiently wide 
clock pulses for the up 
and down counters. 




TIME DELAY 



t>M>4>M> 



12 ap I 



rh 



104 
7404 






^{>M>^ 



r^ 



LOAD [3>- 



I 



DATA [~>- 
INPUT I 
LINES Q>- 
I 

np>- 
I 



o- 
I 

I 

o- 

I 
I 

I 



t^M^H^^-^ 



rf7 



.001 "-2 

7404 



(A + B)D 



IC6 
7408 



6a V 



TTXi 






U 



10 



IC7 
4 74193 



Vd 

LD 

A 

B 

C 

D 



ON 
OA 
08 
OC 
CD 
CL 

GND 



CAR BOL 



L 



14 






I 

o 

I 

I 

I 



IDATA 



OUTPUT 



Vd 

LD 

A 

B 

C 

D 



ON 
OA 
OB 
OC 
OD 
CL 

GND 



(TO 
3 I COMPUTER) 

IC8 I 

74193 



I 



I 
I 

I 

-o 

I 



/77 





-U .DATA 

/77 Iqutput 
Kto 
I computer) 



78 July 1978©BYTE Publications Inc 




Personal Computers 
& Microprocessing 

Here are two inexpensive programmed 
learning courses designed to keep 
you up-to-date in digital electronics. 



Design of Digital Systems - six volumes 



The products of digital electronics techno- 
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ADVANCED COURSE 
DESIGN OF DIGITAL SYSTEMS 

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CONTENTS 

The contents of Design of Digital Systems 
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Book 1: Octal, hexadecimal and binary 
number systems; representation of negative 
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Book 2: OR and AND functions; logic 
gates; NOT, exclusive-OR, NAND.NOR and 
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Digital Computer Logic & Electronics 

CONTENTS 

Digital Computer Logi: and Electronics is 
designed for the beginner. No mathmetical 
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assumed, though you should have an aptitude 
for logical thought, it consists of 4 volumes- 
each 1 r/2" X 8%"— and serves as an intro- 
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Contents include: Binary, octal and decimal 
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systems; AND, OR, NOR and NAND gates 
and inverters; Boolean algebra and truth 
tables; DeMorgan's Laws; design of logical 
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flops; binary counters, shift registers and 
half-adders. 



^ 



GFN Industries, Inc. 
Suite 400-B 
888 Seventh Ave. 
New York 
N.Y. 10019 



Call TOLL-FREE (800)331-1000 

(orders only) 



BYTE luly 1978 79 



Octal 
Address 


Operation 
Codes 


001 000 
001 002 


066 
056 


aaa 
bbb 




001 004 


101 






001 005 
001 006 


310 
107 






001 007 
001 010 
001 Oil 


320 
101 
271 






001 012 
001 015 
001 016 


110 
107 
272 


004 


001 


001 017 
001 022 


110 
277 


004 


001 


001 023 
001 026 
001 031 


140 
110 
301 


047 
054 


001 
001 


001 032 


061 







Commentary 

set memory address 
registers to location 
of high byte of 
desired position 
get low byte of 
current position 
save in B register 
get high byte of 
current position 
save in C register 
read low byte again 
compare to previous 
read 

re-read if not same 
read high byte again 
compare to previous 
read 

re-read if not same 
compare high byte 
with desired high byte 
jump if less 
jump if greater 
high byte equal-recall 
low byte to A 
decrement address 
registers to point to 
low byte of desired 
position 

compare low byte to 
desired low byte 
jump if less 
jump if greater 
equal, set A for 
DIR and GO = 
go output DIR & GO 
position low — set 
GO = 1, DIR = 
go output GO & DIR 
position high — set 
GO= I.DIR = 1 
output GO and DIR 



Listing 1: Intel 8008 program for motor control. This segment 
of code should be executed at least 20 times per second. The 
desired position is in location bbb-aaa (high byte) and the next 
previous location (low byte). The two locations must be on the 
same page. Input port is the low byte of the counter and port 
3 is the high byte. Output port has DIR in its least significant 
bit and GO in the next bit. 



001 033 277 



Mnemonic 

LLI aaa 
LHI bbb 



READ INP 

LBA 
INP 3 

LCA 
INP 
CPB 

JFZ READ 
INP 3 
CPC 

JFZ READ 
CPM 

JTC LOW 
JFZ HIGH 
LAB 

DCL 



CPM 



001 
001 
001 


034 
037 
042 


140 047 
110 054 
006 000 


001 
001 




JTC LOW 
JFZ HIGH 
LAI 


001 
001 


044 
047 


104 056 
006 002 


001 


LOW 


JMP OUT 
LAI 2 


001 
001 


051 
054 


104 056 
006 003 


001 


HIGH 


JMP OUT 
LAI 3 


001 


056 


127 




OUT 


OUT3 



Figure 7: Program flow- 
chart Variables DU and 
DL hold the upper and 
lower bytes of the de- 
sired position. This pro- 
gram must be executed at 
least 20 times per second. 
If the motor runs away, 
complement the DIR bit 
outputs. Do not attempt 
to reach positions closer 
than 50 turns to or 
65535 with this algorithm 
because of the counter 
overflow which occurs. 



the desired position. Such a scheme would 
reduce the settling time of the system to a 
minimum. 

Modifications 

For those purists who insist on doing 
everything in software, the Schmitt trigger 
outputs may be tied directly to two com- 
puter input lines, or even interrupt lines, and 
the decoding and counting may be done in 
the computer. For those other purists who 
prefer not to tie their machine up with 
repetitive loops such as the one in figure 7, 
this positioning scheme may be implemented 
in hardware by installing four 4 bit compara- 
tors on the counter outputs. Cascade the 
comparators together and connect two 
output ports from a computer to the other 
comparator inputs. Invert the "equal" 
comparator output and connect it to GO. 
Connect the "greater than" comparator 
output to DIR. If the motor runs away 
connect the "less than" comparator output 
to DIR. Now the computer outputs 16 bit 
position values and the circuit positions the 
motor to follow the computer output." 



( BEGIN J 









. 






NPUT LOWER 
BYTE OF COUNTER 
INTO LI 




1 




INPUT UPPER 
BYTE OF COUNTER 
INTO Ul 




1 


' 


INPUT LOWER 
BYTE OF COUNTER 
INTO L2 




1 




INPUT UPPER 
BYTE OF COUNTER 
INTO U2 


— 


5!0</li.l2\ 

|YES 

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THE 1st FULL DAY INDUSTRY TRADE SHOW AUG. 24th 



I Personal 
C Computing 



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^ •A Full Day To See Your Suppliers, Dealers, Distributors 
^0«^ • New Products and New Manufacturers 

• Plus Three Additional Days 

• Aug. 25th-27th, Personal Computing Show 




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BYTE July 1978 81 



r 



Books to Make the Summer 



Just 
Arrived I 



_The Cheap Video Cookbook, the latest in Don Lancaster's series of hardware books, 



Cheop 
Video , , 

coo«ei<3©i>c 

Ij ± 



I ifl 



continues where the TV Typewriter Cookbook leaves off. New, inexpensive video display 
circuits (and the software to drive them) are described. The designs allow a variety of alpha- 
numeric and graphics formats to be implemented, including high resolution graphics. The 
circuits are designed for use on 6500 or 6800 systems, but can be adapted to other proces- 
sors. Chapters also cover methods for displaying memory contents and a description of 
transparency techniques. 256 pp. $5.95. 

BASIC: A Hands-on Method by Herbert D Peckham is a light-hearted but thorough 

self-study course in BASIC, designed for people new to the subject. The introduction 
defines what BASIC is, gives some background on its origins, and tells you how to get 
started. Chapters cover: computer arithmetic and program management; input, output 
and simple applications; decisions and branching; looping; working with collections of 
numbers; subroutines; and more. Although the book is oriented towards the implementation 
of BASIC on time sharing terminals, the ideas and techniques are applicable to the personal 
computer. 244 pp. $7.95. 



Not Just a Good Buy But An Investment 



Microprocessor Lexicon, Acronyms 

and Definitions by SYBEX. 1 10 pp. This 
little book is a necessity to anyone who 
wants an explanation of those hard-to- 
fathom acronyms and other micro terms. 
Included are sections on signals in the 
main standards, functions of essential 
chips, and more. At 414" x 5Vs" it can be 
pocketed easily. For only $2.95 every 
microcomputerphile should have a copy. 




The 8080 Programmer's Pocket 

Guide written by Sceibi Computer 
Consulting Inc is a handy 3" x 4" com- 
pendium of 8080 facts. Included are 
detailed descriptions of the 8080 in- 
struction set, information about an 8080 
paper tape loader program, and an in- 
struction set summary and index. 8080 
programmers will want a copy of this 
useful book. 130 pp. Only $2.95. 



jT^iS^^ 




Computer Science: A First Course, Second Edition, by Forsythe, Keenan, Organick, 

and Stenberg. Over 760 pp. $18.25 hardcover. 

Computer Science: Projects and Study Problems by A I Forsythe, E I Organick, and 

R C Plummer. This companion text to Computer Science: A First Course is a series of work 
problems designed to intrigue the reader. Problems include plotting graphs, simultaneous 
equations, the eight queens problem, designing a perceptron (a machine that learns), as well 
as a series of problems specifically designed to complement the chapters of Computer 
Science: A First Course. 292 pp. $9.75. 

Computer Science: Programming in FORTRAN IV by A I Forsythe, R M Aiken, 

C E Hughes, and E I Organick. This supplement to Computer Science: A First Course, 
Second Edition, shows how to turn flowcharts into equivalent FORTRAN programs. Fea- 
tures include chapters on FORTRAN 10 statements, assignment statements, rounding, 
formatting, subroutines, practical applications, etc. The advent of FORTRAN software 
packages for small systems makes this a timely addition to the literature. 210 pp. $5.25. 

The TTL Data Book for Design Engineers, Second Edition, by Texas Instruments is a 



> Supplement to 

I The TTL 



^ 



BITS 



.( current source of information on the design specifications and characteristics of the Texas 

Instruments 7400 series of devices. In it you'll find a complete section of 7400 series pinout 
diagrams at the front, plus the usual detailed descriptive information on the more compli- 
cated circuits. How do you find out what a 74412 does? Turn to its pinout diagram on page 
5-74, then vector to the detail information on page 7-502 where you discover that it's Texas 
Instruments' version of the Intel 821 2 part. 828 pp. Only $4.95 hardcover. 

Supplement to the TTL Data Book for Design Engineers, Second Edition, by Texas 

Instruments. As the name implies, this supplement brings your Texas Instruments TTL 
Data Book up to date with the latest information about new TTL devices. The 56-page 
book includes information about synchronous counters, function generators, and many 
other devices. $1.25. 

The Microcomputer Bookstore 



82 BYTE |ulv 1978 



■^ 



Last All Year Long 



BASIC with Business Applications by Richard W Lott focuses on the BASIC language 

and its application to specific business problems. The book is divided into two sections. Part 
one introduces the BASIC language and the concept of logical flowcharting. Part two pre- 
sents problems and possible solutions. Topics include: interest rate calculation, break-even 
analysis, loan rates, and depreciation. Exercises at the end of each chapter give a greater un- 
derstanding of BASIC by actual programming. This book is a great aid to the beginner want- 
ing to learn BASIC without having a technical or scientific background. 284 pp. $10.50. 

Financial Analysis and Business Decisions on the Pocket Calculator by Jon M Smith is 

designed to aid the experimenter in performing applied analysis. It gives a variety of numeri- 
cal techniques, approximations, tables, graphs, and flowcharts for calculations. All methods 
have been optimized for the pocket calculator, and the book stresses the use of the business- 
type calculator having the usual complement of business functions. Topics include: calcu- 
lating present and future values, consumer finances, real estate calculations, business statis- 
tics, and systems analysis. 317 pp. An invaluable source tool at $14.95 hardcover. 

Charging for Computer Services by D Bernard, J C Emery, R L Nolan, and R H Scott 



Business 



is written for managers who must deal with service charges. This book provides the manager 
with principles and guidelines for a better understanding of the charge problem. The book 
provides general design principles along with specific suggestions to deal with specific prob- 
lem areas. Charging for Computer Services is a necessary book for the manager who must 
make decisions in this vital area. 120 pp. $10.00 hardcover. 




A.I. 



Introduction to Artificial Intelligence by Philip C Jackson Jr surveys the field be- 
ginning with Turing's test, the mathematical description of phenomena, finite state ma- 
chines and limits to computational ability, followed by chapters on problem solving, game 
playing, pattern perception, theorem proving, semantic information processing, parallel 
processing, evolutionary systems, robots, and a look at the future of the field. This thought- 
ful and unusual book will make a useful addition to your library. A 50-page bibliography is 
included. 453 pp. $18.50 hardcover. 






r 



Just Out! 



Howi to Build a Computer-controlled Robot by Tod Loofbourrow. This book combines 

the dream of robotics— to create an intelligence other than human— with the reality, by pro- 
viding both hands-on experience with robotics and an application of a microprocessor. You 
can learn the fundamentals while utilizing the ultimate in current hobby computer technol- 
ogy. This book details the step-by-step directions for building a robot, named "Mike," con- 
trolled by a KIM-I microprocessor, with the complete control programs clearly written out. 
Photographs, diagrams, and tables help to direct you in the construction. $7.95. 



BITS 



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BYTE liriy 1978 83 



A Short History of Computing 



Keith S Reid-Green 

Director, Software Systems Development 

Educational Testing Service 

Princeton NJ 08540 




A few weeks ago a master's degree candi- 
date in computer science confided, with an 
embarrassed laugh, that he had never seen a 
computer. His experience with the machines 
of his chosen vocation had consisted entirely 
of submitting punched cards through a hole 
in a wall and later getting printed results the 
same way. While his opportunities to see 
equipment are restricted due to his student 
status, there are also thousands of working 
programmers and analysts using large scale 
equipment who have no contact with 
existing hardware and will never have a 
chance to see any first or second generation 
computers in operation. 

This is in sharp contrast with the way 
programmers worked in the late 1950s and 
early 1960s. Before 1964, when multipro- 
gramming computers were introduced, the 
typical programmer had opportunities to 
come in contact with the computer if he or 
she wanted to do so. Prior to 1960, in fact, 
most programmers actually operated the 
machine when debugging their programs. 
These people learned of the computer as a 
physical device; the current programmer is 
more likely to think of it as a vague logical 
entity at the other end of a terminal. Thus, 
many large system programmers have the 
rare distinction of using a tool without 
knowing how it works or what it looks like. 
This is in spite of the fact that many im- 
portant computer developments have 



Photo 1 : A Chinese abacus. 



Photo Acknowledgements 

Photos 1 and 3 courtesy of Bettmann Archive, 
New York. 

Photos 2, 4, 5, 6, 7, and 8 courtesy of the IBM 
Corporation. 

Photo 9 courtesy of Cray Research Inc. 
Photo 10 courtesy of the Sperry Rand Corpor- 
ation. 



84 July 1978 © BYTE Publications Inc 




Photo 2: Pascal's adding machine. Note that the rightmost dial has 12 positions and its neighbor has 20. The machine was in- 
tended for calculations involving the French currency of the period. 



occurred within the average programmer's 
lifetime. 

However, in the past year or two, dra- 
matic reductions in the cost of minicom- 
puter components and the advent of the 
microcomputer have returned the hands-on 
computer to respectability in two ways. 
First, it is now possible to justify hands-on 
debugging on a small computer, since the 
hourly rate of the programmer is higher 
than that of the machine. Second, the 
decreasing cost of home computing has 
fostered the birth of a new class of "renais- 
sance programmers": people who combine 
programming expertise with hardware know- 
ledge and aren't afraid to admit it. Renais- 
sance programmers can learn much from the 
lessons of computer history; simple and 
inelegant hardware isn't necessarily best, 
but it's frequently cheapest. 

In short, the stored program computer 
became a necessary tool only recently, even 
though various mechanical aids to compu- 
tation have been in existence for centuries. 



One of the first such aids was the abacus, 
the invention of which is claimed by the 
Chinese. It was known in Egypt as early as 
460 BC. The Chinese version of the abacus 
(as shown in photo 1) consists of a frame 
strung with wires containing seven beads 
each. Part of the frame separates the top- 
most two beads from the lower five. The 
right-hand wire represents units, the next 
tens, the next hundreds, and so on. The 
operator slides the beads to perform addi- 
tion and subtraction and reads the resulting 
sum from the final position of the beads. 
The principle of the abacus became known 
to Roman and early European traders, who 
adopted it in a form in which stones (called 
by the Latin calculi, hence the word "calcu- 
late") are moved around in grooves on a flat 
board. 

The use of precision instruments dates 
back to the Alexandrian astronomers. Like 
the mathematics of the period, however, the 
development of scientific instruments died 
away with the demise of the Alexandrian 



July 1978 @ BYTE Publicitiom Inc 85 



school. The Arabs renewed interest in 
astronomy in the period between 800 and 
1500 AD, and it was during this time that 
the first specialists in instrument making 
appeared. The center of instrument making 
shifted to Nuremberg, beginning about 
1400. By the middle of the 16th Century, 
precise engraving on brass was well advanced 
due in part to the interest in book printing. 

Calendrical calculators used for deter- 
mining the moon's phases and the positions 
of the planets crop up in all the major 
periods of scientific thought in the past two 
thousand years. Parts of a Greek machine 
about 1800 years old, apparently used to 
simulate the motions of the planets, were 
found in 1902 in the remains of a ship off 
the island of Antikythera. The gears of the 
machine indicate amazing technical ability 
and knowledge. Later calendrical calculators, 
which were usually of the type in which two 
or more flat disks were rotated about the 
same axis, came to include a means of telling 
time at night by visually aligning part of the 
Big Dipper with the pole star. 

Trigonometric calculators, working on a 
graphical principle, were in use in the Arabic 
period. Such calculators were used mainly 
to determine triangular relationships in 
surveying. The popularity of this device was 
renewed in 14th Century Europe; in fact, 
calculating aids of all kinds grew rapidly in 
popularity as well as in scope from this time 
onward, largely due to the difficulty of the 
current arithmetic techniques. Napier was 
continually seeking ways to improve com- 
putational methods through his inventions. 
One such invention, "Napier's bones," con- 
sisted of a number of flat sticks similar to 
the kind now used in ice cream bars. Each 
stick was marked off into squares containing 
numbers. To perform calculations, the user 
manipulated the sticks up and down in a 
manner reminiscent of the abacus. Of parti- 
cular interest is the fact that Napier's inven- 
tion was used for general calculation at a 
time when many other devices were used for 
the specific determination of one measure- 
ment, such as the volume of liquid in a 
partly full barrel, or the range of an artillery 
shot. 

Pascal invented and built what is often 
called the first real calculating machine in 
1642 (shown in photo 2). The machine 
consisted of a set of geared wheels arranged 
so that a complete revolution of any wheel 
rotated the wheel to its left one tenth of a 
revolution. Digits were inscribed on the side 
of each wheel. Additions and subtractions 
could be performed by the rotation of the 
wheels; this was done with the aid of a 
stylus. Pascal's calculator design is still 



widely seen in the form of inexpensive 
plastic versions found in variety stores. 

In 1671 Leibniz invented a machine 
capable of multiplication and division, but 
it is said to have been prone to inaccuracies. 

The work of Pascal, Leibniz, and other 
pioneers of mechanical calculation was 
greatly facilitated by the knowledge of gears 
and escapements gained through advances in 
the clock. In the 13th Century, a clock was 
devised for Alfonso X of Spain which used a 
falling weight to turn a dial. The weight was 
regulated by a cylindrical container divided 
into partitions and partly filled with mer- 
cury. The mercury flowed slowly through 
small holes in the partitions as the cylinder 
rotated; this tended to counterbalance the 
weight. By the 15th Century, the recoil of a 
spring regulated by an escapement had made 
its appearance as a source of motive power. 
Gear trains of increasing complexity and 
ingenuity were invented. Clocks could now 
strike on the hours, have minute and second 
hands (at first on separate dials), and record 
calendrical and astronomical events. Gears 
opened the door to wonderful automata and 
gadgets such as the Strasbourg clock of 
1354. This device included a mechanical 
rooster which flapped its wings, stretched 
its metal feathers, opened its beak and 
crowed every day at noon. Later, important 
improvements in timekeeping included 
Galileo's invention of the pendulum; and the 
accurate driving of a clock without weights 
or pendulum which led to the portable 
watch. 

Although mechanical and machine shop 
techniques still had a long way to go (con- 
sider the 19th Century machinist's inability 
to fit a piston tightly into a cylinder), the 
importance of mechanical inventions as aids 
to computation was overshadowed by 
electrical discoveries beginning with the 
invention of the battery by Volta in 1800. 

During the 1700s, much experimental 
work had been done with static electricity. 
The so-called electrical machine underwent a 
number of improvements. Other electrical 
inventions like the Leyden jar appeared, but 
all were based on static electricity which 
releases very little energy in a very specta- 
cular way. In 1820, following Volta's dis- 
covery. Oersted recognized the principle 
of electromagnetism that allowed Faraday to 
complete the work leading to the dynamo, 
and eventually to the electric motor. It was 
not until 1873, however, that Gramme 
demonstrated a commercially practicable 
direct current motor in Vienna. Alternating 
current (AC) was shown to be the most 
feasible type of electric power for distri- 
bution, and subsequently the AC motor was 



86 July 1978 £> BYTE Publications Inc 



GAMES 
COMPUTERS 



Chess Skill in Man and Ma- 
chine edited by Peter W Frey. 
This is a most challenging book, 
concerning itself with the when, 
how, and why of computer chess. 
217 pp. $14.80 hardcover. 

Game Playing with Com- 
puters by Donald D Spencer. 
Read this book for an Introduc- 
tion to numerous recreational 
uses of the computer. Topics in- 
clude mathematical problems, ca- 
sino games, board games, unusual 
gambling games, and logic games. 
Many BASIC language programs 
and listings are included to show 
details. 312 pp. $16.95 hardcover. 

What to do After You Hit 

Return or PCC's First Book of 
Computer Games. This is PCC's 
first book of computer games, a 
compendium of computer games, 
including listings of 37 selected 
BASIC games. 1 70 pp. $8.00. 

BASIC Computer Games: 

Microcomputer Edition edited by 
David H Ahl. Here are 102 classic 
computer games, every one in 
standard microcomputer BASIC; 
every one complete with large leg- 
ible listing, sample run and des- 
criptive notes. All the classics are 
here: Super Star Trek, Football, 
Blackjack, Lunar Lander, Tic Tac 
Toe, Nim, Life and Horserace. 
This revision of 101 BASIC Com- 
puter Games is a must even if you 
own the original. 185 pp. $7.50. 

The Best of Creative Com- 
puting Volume I. 

The Best of Creative Com- 
puting Volume II 

Culled from the pages of 
Creative Computing Magazine, 
these two volumes provide fic- 
tion, fun, foolishness, and plenty 
of nuts and bolts commentary 
and programming information for 
anyone curious or serious about 
the wonderful world of personal 
computing. $8.95 per volume. 



PLAY 




Just Arrived*. 



Chess and Computers by 

David Levy. If you enjoy playing 
chess, then you will thoroughly 
enjoy Chess and Computers. This 
145-page book is loaded with 
chess games played by and with 
computers. When you settle down 
with this book, it would be a 
good idea to set up your chess 
board and play the games. Half 
the enjoyment is found in playing 
along, duplicating the moves, 
reading the comments by the au- 
thor and adding your own com- 
ments. $8.95. 

Game Playing With BASIC 

by Donald D Spencer lets you en- 
joy the challenge of competing 
with your own computer. Games 
described include: 3D Tic Tac 
Toe, Nim, Roulette, Slot Ma- 
chines, Magic Squares, Keno, 
Morra, Baccarat, Knight's Magic 
Tour, and many others. The style 
is nontechnical, and each section 
gives complete rules for the game, 
how it works, illustrative flow- 
charts, and example outputs for 
each program. The last chapter 
contains 26 games for reader solu- 
tion, including Hexapawn and 
Poker Dice. 166 pp. $6.95. 

57 Practical Programs and 

Games in BASIC by Ken Tracton 
is just that: a collection of practi- 
cal BASIC applications programs 
for experimenters, students and 
professionals. In addition to the 
more conventional programs, 
there are several unusual ones 
(Hydrocarbon Combustion, Inter- 
active Growth Patterns, Vector 
Cross Product, and Pi-Network 
Impedance Matching, to name a 
few). The book includes many 
flowcharts and diagrams to aug- 
ment the text and programs. 
204 pp. $7.95. 



BITS 



Circle 35 on inquiry card. 



T.M. 



For your convenience in ordering, please use this page plus the order 
form on page 83. You may photocopy this page if you wish to keep 
your BYTE intact. 

CALL BANK CARD ORDERS TOLL FREE 1-800-258-5477. 

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BYTE July 1978 87 




Photo 3: The Jacquard loom, one of the first machines to use holes punched In cards to control Its actions. 



88 luly 1978 e BYTE Publications Inc 



invented in 1 888 by Tesla. The value of elec- 
tric power for transportation was quictcly 
recognized and employed in tramways and 
electric railways. This led to improvements 
in methods for controlling electricity. Elec- 
tric lighting methods sprang up like weeds 
during the latter half of the 19th Century. 
The most successful were due to the efforts 
of Swan in England and Edison in the 
United States. Work on electric lighting, the 
telegraph and the telephone led to the 
wonder of the age: radio. In 1895, Marconi 
transmitted a radio message over a distance 
of one mile, and six years later from England 
to Newfoundland. 

As a consequence of the rapid growth of 
interest in the radio, much work was done 
on the vacuum tube. Lee de Forest dis- 
covered the principle of the triode in 1907. 
Until the development of the transistor, the 
vacuum tube was the most important device 
in computer technology due to its ability to 
respond to changes in electrical voltage in 
extremely short periods of time. The 
cathode ray tube, invented by William 
Crookes, was used in computers for a few 
years prior to 1960. It faded temporarily 
from view but returned in 1964 due to 
advances in technology that improved its 
economic feasibility as well as its value as 
a display tool. In 1948 Bardeen, Brattain 
and Shockley developed the transistor, 
which began to replace the vacuum tube in 
computers in 1959. The transistor has many 
advantages over the vacuum tube as a com- 
puter component: it lasts much longer, 
generates much less heat, and takes up less 
space. It therefore replaced the vacuum 
tube, only to fall prey in turn to micro- 
miniaturization. Of course, the transistor 
principle didn't go away, but the little 
flying saucers with three wires coming out 
of their bases did. 

Oddly enough, one of the most funda- 
mental devices in the early history of com- 
puting predates the electronic computer by 
more than two hundred years. The punched 
card was first used to control patterns woven 
by the automatic loom. Although Jacquard 
is commonly thought to have originated the 
use of cards, it was actually done first by 
Falcon in 1728. Falcon's cards, which were 
connected together like a roll of postage 
stamps, were used by Jacquard to control 
the first fully automatic loom in France, 
and later appeared in Great Britain about 
1810 (see photo 3). At about the same time, 
Charles Babbage began to devote his 
thinking to the development of computing 
machinery. Babbage's first machine, the 
Difference Engine, shown in photo 4, was 
completed in 1822 and was used in the 



computation of tables. His attempts to 
build a larger Difference Engine were un- 
successful, even though he spent £23,000 
on the project (£6,000 of his own, and 
£1 7,000 of the government's). 

In 1833 Babbage began a project that was 
to be his life's work and his supreme frus- 
tration: the Analytical Engine. This machine 
was manifestly similar in theory to modern 
computers, but in fact was never completed. 
During the forty years devoted to the 
project, many excellent engineering drawings 
were made of parts of the Analytical Engine, 
and some parts of the machine were actually 
completed at the expense of Babbage's 
considerable personal fortune. The machine, 
which was to derive its motive power from 
a steam engine, was to use punched cards 
to direct its activities. The Engine was to 
include the capability of retaining and dis- 
playing upon demand any of its 1000 fifty- 
digit numbers (the first suggestion that a 
computing machine should have a memory) 
and was to be capable of changing its course 
of action depending on calculated results. 
Unfortunately for Babbage, his theories 



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Photo 4: The Babbage Difference Engine. 



luly 1978 ® BYTE PuMicitions Inc 89 




Photo 5: The first use of 
punched cards for data 
processing, Hollerith 's card 
sorter dramatically re- 
duced the time required 
to process data collected 
in the 1 890 census. 



were years ahead of existing engineering 
technology, but he contributed to posterity 
the idea that punched cards could be used as 
inputs to computers. 

Herman Hollerith put punched cards to 
use in 1890 in his electric accounting 
machines, which were not computers, but 
machines designed to sort and collate cards 
according to the positions of holes punched 
in the cards (see photo 5). Hollerith's 
machines were put to effective use in the 
United States census of 1890. 

In 1911, the Computing-Tabulating-Re- 
cording Company was formed, which 
changed its name to International Business 
Machines in 1924. In the period between 
1932 and 1945 many advances were made in 
electric accounting machines, culminating 
in 1946 with IBM's announcement of the 
IBM 602 and 603 electronic calculators, 
which were capable of performing arithmetic 
on data punched onto a card and of punch- 
ing the result onto the same card. It was 
Remington Rand, however, who announced 
the first commercially available electronic 



data processing machine, the Univac I, the 
first of which was delivered to the US 
Census Bureau in 1950. In 1963, just thir- 
teen years after the beginning of the com- 
puter business, computer rental costs in the 
United States exceeded a billion dollars. 

Univac I was not the first computer, even 
though it was the first to be offered for sale. 
Several one of a kind computers were built 
in the period between 1944 and 1950 partly 
as a result of the war. In 1939 work was 
begun by IBM on the Automatic Sequence 
Controlled Calculator, Mark 1, which was 
completed in 1944 and used at Harvard 
University (see photo 6). Relays were 
used to retain numbers; since relays are 
electromechanical and have parts that 
actually move, they are very slow by modern 
standards. 

In 1943, Eckert, Mauchly and Goldstine 
started to build the ENIAC (Electronic 
Numerical Integrator and Calculator), which 
became the first electronic computer using 
vacuum tubes instead of relays (see photo 
7). The next year John von Neumann 



90 



luly 197g©BYTE Publicalions Inc 



became interested in EN I AC and by 1946 
had recognized a fundamental flaw in its 
design. In "Preliminary Discussion of the 
Logical Design of an Electronic Computing 
Instrument," von Neumann pointed out 
the advantages of using the computer's 
memory to store not only data but the 
program itself. Machines without stored 
program capabilities were limited in scope, 
since they had to be partly rewired in order 
to solve a new problem (as was the case with 
EN I AC). This process sometimes took days 
during which time the machine could not be 
used. If rewiring of such machines was to be 
avoided, instructions had to be entered and 
executed one at a time, which greatly 
limited the machine's decision making capa- 
bilities. Machines with stored program capa- 
bilities automatically store not only numeric 
data but also the program (which looks like 
numbers and can be treated like numbers) in 
memory. In short, stored program instruc- 
tions can be used to modify other instruc- 
tions, a concept that leads to programs 



which can modify themselves. It is the von 
Neumann stored program concept which is 
universally used in modern computers from 
the smallest microcomputer to the largest 
number crunchers. 

The growth of the missile industry in 
the 1950s greatly stimulated the progress of 
computers used for scientific work. The 
nature of missile data handling at that time 
was such that work loads were very high 
during the week or so after a firing and 
virtually nonexistent in between. Computers 
were too expensive to leave idle, which led 
managers to look for other work for the 
machines. Business data processing grew 
from these roots to its present status, 
accounting for the lion's share of machine 
usage today. 

The latter part of 1959 saw the arrival of 
the transistorized computer. As a conse- 
quence of this innovation, air conditioning 
and power requirements for computers 
were reduced. Several new computers in 
that year were announced by IBM, Control 



Photo 6: IBM's Automatic 
Sequence Controlled Cal- 
culator (ASCC), the Mark 
I, built at Harvard be- 
tween 1 939 and 1944. 






^^?2^^^^; 









Mi>M <W i iW <* W » 






■ »m 





Photo 7: In 1943, Eckert, 
Mauchly, and Goldstine 
started to build the 
EN I A C, Electronic Numer- 
ical Integrator and Calcu- 
lator, which became the 
first electronic computer 
to use vacuum tubes in- 
stead of electromechan- 
ical switches. 



Data Corporation, General Electric, and 
other manufacturers. Among the IBM 
announcements were the 7070 general 
purpose computer; the 7090, a high speed 
computer designed for a predominance of 
scientific work; the 1401, a relatively inex- 
pensive computer aimed at the medium 
sized business and the 1620, a low priced 
scientifically oriented computer. The fan- 
tastic growth of the computer field con- 
tinued through 1961 and 1962 with the 
announcement of more than 20 new 
machines each year. In 1963, continuing 
the family line from the grandfather 704 
(as shown in photo 8), the IBM 7040 was 
announced. This machine embodied many 
of the features of the 7090 at a reduced 
cost. In the same year at least 23 other 
computers were announced by several 
different manufacturers. In 1964, IBM 
announced the 7010, an enlarged and 



Photo 8: The IBM 704 had a core memory capacity of 32 K words with 36 bits per word. Although a card reader, punch, printer, 
magnetic tape drives and drums and a video display were available as peripherals, the concept of simultaneous I O and processing 
was not yet developed. 




92 luly 197gSBYTE Publicilions Inc 



OSBORNE ^ ASSOCIATES, INC. 

The World Leaders In Microprocessor Books 



If you want information on microprocessors, begin with 
the Osborne books. 



ir New prices apply to orders 
postmarked after June 30, 1978 



PROGRAM BOOKS WRITTEN IN BASIC 



Payroll With Cost Accounting 
Accounts Payable And Accounts 

Receivable 
General Ledger 

These books may be used independently, or 
implemented together as a complete ac- 
counting system. Each contains program 
listings, user's manual and thorough docu- 
mentation. Written in an extended version 
of BASIC. 

#22002 (400 pages), #23002* #24002* 
$15.00 ($12.50 prior to July 1, 1978) 

Some Common BASIC Programs 

76 short practical programs, most of which 
can be used on any microcomputer with any 
version cf BASIC. Complete with program 
descriptions, listings, remarks and exam- 
ples, 

#21002 (200 pages) 
$8.50 ($7.50 prior to July 1, 1978) 





AN INTRODUCTION TO MICROCOMPUTERS 

Volume - The Beginner's Book 

If you know nothing about computers, then 
this is the book for you. It introduces com- 
puter logic and terminology in language a 
beginner can understand. Computer soft- 
ware, hardware and component parts are 
described, and simple explanations are given 
for how they work. Text is supplemented 
with creative illustrations and numerous 
photographs. Volume prepares the novice 
for Volume I. #6001 (300 pages) 
$7.95 ($7.50 prior to July 1, 1978) 






Volume I — Basic Concepts 

This best selling text describes hardware 
and programming concepts common to all 
microprocessors. These concepts are ex- 
plained clearly and thoroughly, beginning at 
an elementary level. Worldwide, Volume I 
has a greater yearly sales volume than any 
other computer text. 
#2001 (350 pages) 
$8.50 ($7.50 prior to July 1, 1978) 
Volume II — Some Real Products 
(revised June 1977) 

Every common microprocessor and all sup- 
port devices are described. Only data sheets 
are copied from manufacturers. Major chip 
slice products are also discussed. 
#3001 A (1250 pages) 
$15.00 (no change in price) 



ASSEMBLY LANGUAGE PROGRAMMING 

8080A/8085 Assembly Language Programming 

6800 Assembly Language Programming 

These books describe how to program a 
microcomputer using assembly language. 
They discuss classical programming techni- 
ques, and contain simplified programming 
examples relevant to today's microcom- 
puter applications, 
#31003, 32003 (400 pages each) 
$8.50 each ($7.50 prior to July 1, 1978) 





PROGRAMMING FOR LOGIC DESIGN 

8080 Programming For Logic Design 
6800 Programming For Logic Design 
Z80 Programming For Logic Design 

These books describe the meeting ground 
of programmers and logic designers: written 
for both, they provide detailed examples to 
illustrate effective usage of microprocessors 
in traditional digital applications. 
#4001, #5001, #7001 (300 pages each) 
$8.50 each ($7.50 prior to July 1, 1978) 



OSBORNE & ASSOCIATES. INC. • P.O. Box 2036 • DEPT. 110 -Berkeley, California 94702 • 



See prices above 



6001 Volume — The Beginner's Book 



2001 Volume I — Basic Concepts 



3001 A Volume I! — Some Real Products (1977 edition) 



4001 8080 Programming For Logic Design 



5001 6800 Programming For Logic Design 



7001 Z80 Programming For Logic Design 



31003 8080A/8085 Assembly Language Programming 



32003 6800 Assembly Language Programming 



21002 Some Common BASIC Programs 



22002 Payroll With Cost Accounting 



PRICE 



QTY 



6'/j%, SF Bay Area residents only 

6%, California residents outside SF Bay Area 

Payment by check or money order 

must be enclosed for orders of 

10 books or less. 



TOTAL 

Sates Tax (Calif, residents only) 

Shipping Charges 

TOTAL AMOUNT ENCLOSED 



AMT 



(4151 548 2805 TWX 910 366 7277 

9:00 a.m. - 5:00 p.m. Pacific Time 



CITY STATE ZIP PHONE 

SHIPPING CHARGES 

O 4th class $0.35 per book (allow 3-4 weeks within U.S., not applicable to discounted orders) 
a $0.75 per book. UPS (allow 10 days) in the U.S. 
□ $1.50 per book, special rush shipment by air in the U.S. 
D All foreign orders, $3.00 per book for air shipment 
Shipping for targe orders to be arranged. 



"l^These books are scheduled to be published during 1978. 
Please notify me when they are available: 

D 23002 Accounts Payable and Accounts Receivable 
D 24002 General Ledger 



Please send information on; 

D Becoming an O&A dealer 

D School discounts 

n List of foreign distributors 

F8 



Circle 293 on inquiry card. 



BYTE July 1978 93 




Photo 9: Cray Research Inc has recently introduced their entry into the field 
of supercomputers, the Cray-1 , which can perform between 20 million and 
60 million floating point calculations per second. 



faster version of the 1410, and the 360, 
which came in many different sizes and 
embodied many features not found in 
previous computers. Control Data Corpor- 
ation announced the 6600, and General 
Electric their 400 series. The IBM 360/370 
is typical of a trend in computer manu- 
facturing which is currently followed by 
most manufacturers: upward compatibility. 
In the years prior to 1965, every manu- 
facturer spent huge sums of money on 
research and programming support for 
several types of computers; several went out 
of business doing so. Likewise, computer 
users spent a lot of money to develop their 
systems for a particular computer only to 
find it had been superseded by a faster, less 
expensive machine. As a consequence, the 
deadly management decision of the period 
was, "Do we get the cheaper machine and 
spend the money on reprogramming, or do 
we risk staying with an obsolete computer 
and losing our programmers to the company 
across the street?" 

Current developments point to a new 
trend away from the bigger machines. The 
combination of lower prices for components 
and programmable read only memories is 
attracting many manufacturers to the field 
of minicomputers and microcomputers. The 
current trend is clearly toward the personal 
computer, with TV game microprocessors 
leading the way." 



Photo 10: The UNI VAC I 
computer system was the 
first commercial computer 
produced by Remington 
Rand (now the Sperry 
Univac division of Sperry 
Rand Corporation). The 
first UNIVAC I was sup- 
plied to the United States 
Bureau of the Census in 
March 1951. It was the 
first computer to be 
equipped with extensive 
peripheral equipment. 




94 July 1978 IS BYTE Publiciliom Inc 



Everything you've ever 

^vanted toKnow aJbout 
microconqiuteis in 

ONE conmlete book 

foronfc^ $10.95 



Over 400 pages. Full 8V2" x 11" size. 



The ultimate book 
about microcomputers. 
Written by experts 
. . . SCELBI and BYTE. Over | 

400 pages. A collector's item, \ 

featuring The Basics ~^ " "~ ' *~ 

from the first 16 issues of BYTE and SCELBI's 
classic library of books. Your microcomputer 
bookshelf is incomplete without this priceless edition 




You can't buy information 
organized like this any- 
where. This is the book 
that everyone who is into micro- 
computers needs for reference, 
for ideas, for clues to problem 
solving. It is a truly authorita- 
tive text, featuring easy-to-read, 
easy-to-understand articles by 
more than 50 recognized pro- 
fessional authors, who know and 
love microcomputers from the 
ground up. Logical and com- 
plete, it features many glos- 
saries, and is illuminated with 
profuse illustrations and photo- 
graphs. 

The Scelbi/BYTE Primer is 
divided into four logical sec- 
tions, that take you from point 
"0" through building and pro- 
gramming your own computer. . . 
step-by-step-by-step. 

What can you do with a micro- 
computer? Checkbook balanc- 
ing. Recipe converting and food 
inventory. Heating and air condi- 
tioning control. Home and busi- 
ness security and management. 
Playing the ponies. Analysis of 
the stock market. Maintaining 
massive data banks. Self-instruc- 
tion. Toys and games. Small 
business accounting and inven- 
tory. And lots, lots more. 

Circle 322 on inquiry card. 



How does a microcomputer do 

it? Lots of "how to" theory. In- 
troducing you to microcomputer 
operation. 6800, 6502, Z80 CPU 
chip capabilities. RAM and ROM 
memories. Addressing methods. 

Til 

SSElH/ei'TE 
FIVITIErV 

Over 400 pages. Selected articles 
from BYTE and SCELBI books. 
Profusely illustrated. Many 
photographs. $10.95, plus$1 
shipping and handling. 

How to control peripherals. 
Transmission of information to 
and from computers. Magnetic 
recording devices for bulk stor- 
age. Analog to digital conver- 
sion. How a computer can talk. 
Other I/O techniques. And more. 



Order your copy today! 


SCELBI COMPUTER 




CONSULTING INC. 


BITS 


Post Office Box 133 PP STN 


70 Main Street 


Dept. B 


Peterborough, NH 


Milford, CT 06460 


03458 




1 800 258-5477 



Prices shown for North American customers. 
Master Charge. Postal and bank Money 
Orders preferred. Personal checks delay 
shipping up to 4 weeks. Pricing, specifica- 
tions, availability subject to change without 
notice. 



**«^ 



All about building a micro- 
computer system. Over 12 com- 
plete construction articles. Flip- 
flops. LED devices. Recycling 
used ICs. Modular construction. 
Making your own p.c. boards. 
Prototype board construction. 
Make your own logic probes. 
Construction plans for 6800 and 
Z80 computers. Building plans 
for l/Os — TV and CRT displays, 
cassette interfaces, etc. Mathe- 
matics functions. ROM program- 
mer. Plus much, much more. 

How to program a micro- 
computer. Programming for the 
beginner. Assembling programs 
by hand. Monitoring programs. 
Number conversions. Game of 
Hexpawn. Design your own as- 
sembler. Lots more. 

And that's only the beginning! 
Others have spent millions ac- 
quiring the type of microcom- 
puter information found within 
the 400 pages of The Sceibi/ 
BYTE Primer. But, it costs you 
only $10.95, plus $1 for postage 
and handling, complete! You 
know the quality of Sceibi and 
BYTE. This is your assurance of 
excellence throughout this MUST 
text. Order your copy today! And, 
get one for a friend! 

BYTE |ury 1978 95 



Our MacroFloppy™ 
goes twice the distance. 

For '695. 




Introducing the Micropolis MacroFloppv™:1041 and .1042 disk dnve sub- 
systems. For the S-100/8080/Z-80 bus. Pacl<ing 100% more capacity into a 
5%-inch floppy disk than anyone else. 143K bytes, to be exact. For as little 
as $695. 

The MacroFloppv;1041 comes with the Micropolis Mod I floppy packaged 
inside a protective enclosure (without power supply). And includes an S-100 
controller Interconnect cable, Micropolis BASIC User's Manual, A diskette con- 
taining Micropolis BASIC, and a compatible DOS with assembler and editor 
The :1041 is eyen designed to be used either on your desk top, or to be inte- 
grated right into your S-100 chassis. 

The MacroFloppy:1042 comes with even/thing the :1041 has, and more. 
Such as d.c. regulators, its own line voltage power supply and, to top it off 
a striking cover Making it look right at home just about anywhere. 

Both MacroFloppy systems are fully assembled, tested, burned-in, and 
tested again. For zero start-up pain, and long term reliability. They're also 
backed up by our famous Micropolis facton/ warranty. 

And both systems are pnced just right. $695 for the MacroFloppv:1041 
and $795 for the MacroFloppy:1042. 

You really couldn't ask for anything more. 

At Micropolis, we have more bytes in store for you. 

For a deschptive brochure, in the U.S. call or write Micropolis 
Corporation, 7959 Deehng Avenue, Canoga Park, California 91304. Phone 
(213)705-1121. 

Or better yet, see your local dealer 



Circle 235 on inquiry card 



MICROPOLIS 

More bytes in store for you. 



jIuFisand 
Newsletters 



Conducted by David Wozmak 



The Computer Hobbyist Group of 
North Texas 

The Printed Circuit is a monthly publica- 
tion of The Computer Hobbyist Group of 
North Texas, a nonprofit organization dedi- 
cated to the interests of the personal and 
hobby computer enthusiast. The officers of 
the club are R Neil Ferguson, president; Bill 
Lewis, vice-president; Dave Aos, secre- 
tary, and Ted Palmer, treasurer. Subscription 
to Tlie Printed Circuit may be obtained by 
joining the group at a rate of $7 per year. 
Dues should be sent to Ted Palmer, 1704 
Downey Dr, Fort Worth TX 76112. All 
correspondence regarding 777e Printed Cir- 
cuit should be addressed to POB 1344, 
Grand Prarie TX 75051. 

ACG-N) 

The Amateur Computer Group of New 
Jersey cosponsored the Trenton Computer 
Festival on April 22 thru 23. The show had 
an attendance of just over 2000. There were 
a number of presentations on items of 
interest to the hobbyist. The talks included 
such topics as beginning in personal com- 
puting, software, robotics, amateur radio, 
interfacing, and many special microcom- 
puter applications. The list of speakers in- 
cluded Carl Helmers from BYTE, Sol Libes 



(ACG-NJ), David Ahl (Creative Computing), 
and many others. 

Also featured at the festival was a flea 
market covering more than 5 acres, more 
than 40 exhibition booths, and the MSC 
IEEE Student Paper Finals. 

ACG-NJ is a nonprofit educational corpo- 
ration located in northern New Jersey. 
IVIembership is $5 per year (US and Canada) 
or $12 year (foreign). This fee covers a 
newsletter subscription. ACG-NJ can be 
reached by writing to the Amateur Com- 
puter Group of New Jersey, UCTI, 1 776 
Raritan Rd, Scotch Plains NJ 07076. 

SEMCO 

The Southeastern Michigan Computer 
Organization is a charter member of the 
Midwest Affiliation of Computer Clubs 
(MACC) and is a nonprofit, registered orga- 
nization. The club has many special interest 
groups (SIGs) built around the various com- 
puters: SIG-6800, SIG-HUG (Heath Users 
Group for H8 and H11), SIG-RS (Radio 
Shack TRS-80), SIG-S-100 (IMSAI and 
Altair, S-100 bus), SIG-KIM, SIG-Digital, 
and also SIG-BIG, which is a group for those 
interested in big machines. 

SEMCO puts out a newsletter, 777e Data 
Bus, which has an excellent format. It has 



96 luly 1978 ® BYTE PuWicitiom Inc 



TM 



MetaFloppy 

The Micropolls MetaFloppv™ gives you more than four times the capacity of 
anyone else's 5%-inch floppy Because it uses 77 tracks instead of the usual 35. 

The field-proven MetaFloppy with thousands of units delivered, comes 
in a complete family of models. And, like our MacroFloppy™ family of disk 
drives, MetaFloppy is designed for the S-100/8080/Z-80 bus. 

For maximum capacity choose our new MetaFloppy:1054 system Which 
actually provides you with more than a million bytes of reliable on-line stor- 
age. For less money than you'd believe possible 

The MetaFloppy:1054 comes complete with four drives in dual config- 
uration. A controller Power supply Chassis. Enclosure. All cabling A new BASIC 
software package And a DOS with assembler and editor There's even a built- 
in Autoload ROM to eliminate tiresome button pushing 

If that's more storage than you need nght now, try our 
MetaFloppy:1053, with 630,000 bytes on-line. Or our Meta- 
Floppv:1045, with 315,000 bytes on-line Either way you can 
expand to over a million bytes on-line in easy stages, when you 
need to Or want to 

In other words, if your application keeps growing, we've got 
you covered. With MetaFloppy 

The system that goes beyond the floppy 

For a descriptive brochure, in the U.S call or write Micropolis 
Corporation, 7959 Deenng Avenue, Canoga Park, California 91304 
Phone (213) 703-1121 

Or better yet, see your local dealer 

MICROPOLIS" 

More bytes in store for you. 



goes 
beyond. 




Circle 236 on inquiry card. 



club information, and articles which are 
both informative and entertaining. 

Membership is $10 per year and includes 
the newsletter. For more information write 
to the Southeastern Michigan Computer 
Organization, POB 9578, Detroit Ml 48202. 

Sacramento Microcomputer Users Group 

SMUG meets on the fourth Tuesday of 
every month at 7:30 PM (July 25, August 
22) on 99th St, off Hwy 50, in Sacramento. 
Write to SMUG for exact location or for 
other information at POB 161513, Sacra- 
mento CA 95816. 

Alamo Computer Enthusiasts 

Located in San Antonio, this group meets 
on the fourth Friday of each month at 7:30 
PM in room 104, Chapman Graduate Center, 
Trinity University. Special interest groups 
include the Z-80, 8080, 6800, 6502, North 
Star BASIC, Microsoft BASIC, Teletypes, 
graphics, and process controllers. For more 
information write to the Alamo Computer 
Enthusiasts, 7517 Jonquill, San Antonio TX 
78233. 

The Apple Core 

The San Francisco Apple Users Group, or 



the Apple Core, has been formed, and has 
held three meetings to date. The group was 
organized by Scot Kamins from San Fran- 
cisco in early April 1978. 

Membership regulations are somewhat 
exclusive; members must own or use an 
Apple computer. For more information con- 
tact Scot Kamins, organizer, San Francisco 
Apple Users Group, POB 4816, Main PO, 
San Francisco CA 94101. 

Microprocessing Club of 
Gloucester County College 

Located in Sewell NJ, the Microprocess- 
ing Club of Gloucester County College is 
now up and running. Membership is open to 
students of GCC and honorary membership 
is open to all (however, honorary members 
cannot vote). To find out more about this 
club contact Mike Seller, Microprocessing 
Club, Gloucester County College, Tanyard 
Rd, Sewell NJ 08080. 

NECS 

The New England Computer Society 
meets monthly at the Mitre Corp cafeteria, 
Bedford MA. For information write to the 
New England Computer Society, POB 198, 
Bedford MA 01730.* 



J uly 1 978 © B YTE PuUicitiora Inc 97 



jispcis's 

Qipcuif 

QgIIsp 



Build a Keyboard 
Function Decoder 



Steve Ciarcia 

POB 582 

Glastonbury CT 06033 



Figure 1 : Sample hardware 
circuit to decode a single 
control code (in this case, 
CONTROL R). The pulse 
output width is the same 
as that of the key pressed 
strobe. 



KEY-PRESSED 
STROBE 



ASCII CONTROL R 
BINARY CODE 



' B6 [3>- 

85 I >— 

, B4|3>- 

BJ I ^>— 

BZ I ^>— 

I Bo[;[>- 

Bl [3>- 



"Dear, when you go downstairs would 
you turn the printer on for me?" 

IVly wife Joyce was on her way to the 
basement with an armload of photographic 
supplies. "And could you see if I turned the 
video display off as well?" 

I was reclining in an overstuffed chair 
with the keyboard in my lap. Joyce stopped 
at the doorway and said, "Who was your last 
servant?" 

"Please do it for me, honey," I said, 
chastened. "I have papers all over my lap 
and you wouldn't want me to spill my mar- 
tini, would you?" 

"Hey, kid, I thought computers were sup- 
posed to make life easier for us poor folk." 

"They do! It's the peripherals that don't." 

The next logical question I asked myself 
was: why shouldn't turning the printer or re- 
corder on and off be as easy to do as any 
other computer transaction? A couple of 
quick solutions came to mind. One is to 
install an intercom system and station a 
person next to the computer while the re- 
mote terminal is in operation. 

A second and more practical alternative 
is to put long extensions on the power lines 
of your peripherals and apply power to them 
from a remote location, but this means re- 
wiring your house if the computer is down- 
stairs and the terminal is upstairs (as in my 
case). 

The third and probably best approach is 



^ 



3 r>s. 4 3 



■^ 



sr^ 8 6 



II ^-^ 10 12 



'^ 




IT' 



to use some of the unused functions on your 
keyboard to control peripherals remotely. 
There are a number of unprinted characters 
on a keyboard such as: end of transmission, 
end of text, or device control codes. By at- 
taching an ASCII decoding circuit to moni- 
tor the line between the keyboard and the 
computer, these functions can be isolated 
and utilized as peripheral device control sig- 
nals — more about this later. 

The ASCII Code 

Most keyboards use ASCII coding, a 7 bit 
binary code with an eighth bit sometimes 
added for parity checking. (Here we ignore 
the proposed extensions to the officially de- 
fined ASCII code which makes it a true 8 bit 
code or nine bits with parity.) A complete 
list of ASCII codes is outlined in "Complete 
ASCII" by Dave Ciemiewicz (February 1978 
BYTE, page 19). When your computer pro- 
gram is executing and awaiting data from the 
keyboard, a special keyboard input routine 
is usually activated in the program. The sub- 
routine first determines whether a key has 
been pressed by checking for a key-pressed 
strobe signal. On systems that do not check 
parity (and thus use only 7 bit ASCII), the 
eighth bit of an input port is often set as the 
strobe bit. The other seven bits are not con- 
sidered unless thfs strobe bit is "true." When 
this is the case, the seven bits are compared 
to a valid entry table within the program to 
determine what to do with the input. If 
there is no valid comparison, the input key 
does nothing. 

The software read and compare routine 
is analogous to a hardware address decoder. 
For a particular ASCII code like CONTROL 
R hexadecimal 12, a circuit such as that in 
figure 1 could be used to decode and iden- 
tify only this particular code. For routine 
uses such as a hardware reset, this is the way 
many computer experimenters decode an 
ASCII code. This basic circuit can be dupli- 
cated many times to decode other codes. 
Figure 2 illustrates how this approach can 
enable a CONTROL R to turn on a device 



98 



luly 1978 ©BYTE Publicilions Inc 



Wait No Longer! 

The new educational programs are here. 



■pviscover how to get more out of 
■'-' your computer. 

Magnemedia has produced the 
innovative line of software pro- 
ducts you've been waiting for. 
Designed for use both at home or 
in the classroom, these programs 
make learning an exciting ex- 
perience. 

This software comes in hand- 
some two-cassette albums. Each 
cassette provides voice instruc- 
tion on one side and a machine 
readable code on the other. 
Separate instruction booklets are 
provided in non-technical 
language. 

All software is for APPLE II. 
Programs available for other 
micro computers indicated by 
following key: 

• RADIO SHACK TRS-80 

(Level II) 

T^ COMMODORE PET 

^ HEATH H8 (Extended 

Basic) 

Programs Now Available 

• Quiz Baseball (16K)— An ex- 
citing game for two teams or 
players, using your questions. 
Computer simulates action, total- 
ing batting averages and scores. 

• Save-A-SketchTM(8K) — 
Create a colored picture with your 



Arizona 
Personal Computer Place, Mesa (602) 833-8949 

Arkansas 
Datacope. Little Rock (501) 666-8588 

California 
A-Vidd Electronics Co., Long Beacti (213) 598-0444 
Byte Stiop, Marina Del Rey (213) 530-3860 
Byte Stlop, Tustin (714) 731-1686 

Byte Stiop Computer Store, Walnut Creek (415) 933-6253 
Byte Sfiop No. 8, Hayward (415) 537-2983 
Computerland, El Cerrito (415) 233-5010 
Computerland, Lawndale (213) 371-4010 
Computerland, Mission Viejo (714) 770-0131 
Computerland of West L.A., Inglewood (213) 776-8080 
Computers Are Fun, Los Angeles (213) 475-0566 
Recreational Computer Ctrs, Sunnyvale (408) 735-7480 
Ttie Computer Store, Santa Monica (213) 451-0713 

Colorado 
Ttie Byte Shop. Inc., Englewood (303) 761-6232 

Connecticut 
Computerland, Fairfield (203) 374-2227 

Florida 
Byte Stiop, Miami (305) 264-2983 
Georgia 
Byte Sflop, Atlanta (404) 255-8984 
Datamart Inc., Atlanta (404) 266-0336 



computer keyboard. Save it for 
your gallery or use it as an il- 
lustration in another computer 
program. 

• Save-A-StoryTM (16K)— Write 
or copy a story for practice in typ- 
ing, speed reading, or for storage 
in your computer library. 

• Learning Basic (16K) — A 
package of two cassettes with 
multiple programs. Learn pro- 
gramming the easy way— let the 
computer teach you. 

• Mystery WordTM(8K)— De- 
velop your logic skills by guess- 
ing the secret word. Computer 
tells you how many letters are 
correct in each guess. 

• Reverse (8K)— A challenging 
math game that's a real brain 
teaser. How many times will you 
have to switch the numbers to get 
them in proper order? 

• SupermathTM (16K)-The 
computer teaches you to add, sub- 
tract, multiply and divide on your 
own level— in color! 

• True/False Quiz (8K)* i^ ^ — 
Tells you how to enter your own 
quiz. 

• Variable Message (8K)tV — 
You choose message and colors, 
the computer does the rest. 

• Matching Quiz (8K) • —Three 
changeable categories in each pro- 
gram. Match item on left correct- 
ly with one on right and they both 



FAuthorized Distributors! 



Computerland of Atlanta, Smyrna (404) 953-0406 

Illinois 
Byte Shop, Champagne (217) 352-2323 
Computerland, Arlington Heights (312) 255-6488 
Imperial Computer Systems, Rockford (815) 226-8200 

Kansas 
Personal Computer Center, Overland Park (913) 649-5942 

Louisiana 
Computer Shoppe, Metairie (504) 454-6600 

Maryland 
Computerland, Rockville (301) 948-7676 

Massachusetts 
The Computer Store, Burlington (617) 272-8770 

Michigan 
Computerland of Grand Rapids, Kentwood (616) 
942-2931 

New Hampshire 
Computerland. Nashua (603) 889-5238 

New Mexico 
Interactive Computers, Santa Fe (505) 892-9997 

__ Write to: .. 

Magnemedia 

17845 Sky Park Circle, Suite H 
Irvine, CA 92714 (714) 549-9122 



disappear. 

• Don't FallTM (8K)^-The 
computer chooses a word— you 
try to guess the letters without 
falling off cliff. Then you give the 
computer a word. 

• Memory Aide (8K)^— Help 
memorizing facts, verses, lists. 
Computer prompts you, asks you 
to provide missing words, etc. 

• Study Aide (8K)— The com- 
puter gives questions in random 
order. If you miss, it saves the 
question for a later try. 

• Keyboard Organ (4K)— Turn 
your computer into a musical in- 
strument. Play the keys hke a 
piano! 

• Grading Routine (16K) — 
Takes the drudgery out of finding 
class curves. Different categories, 
grading scales, etc. 

• Drawing (4K)*i5r.^ — 
Computer picks word at random 
from list you supply. 

Here's the best news of 
all— each package of two pro- 
grams sells for only $12.00! In- 
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for $7.50. 

Magnemedia software is in 
stock at computer stores 
everywhere. (Dealers listed 
below). If not available yet at 
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you. 



New Jersey 
Computer Corner, Pompton Lanes (201) 835-7080 
The Computer Emporium, Cherry HIM (609) 667-7555 

New Vorii 
Computer Shop of Syracuse, De Witt (315) 446-1284 
Computer Tree Inc., Endwell, (607) 748-1223 
Computer Micro Systems, Manhasset (516) 627-3640 

North Carolina 
Byte Shop, Raleigh (919) 833-0210 

Ohio 
21st Century Shop, Cincinnati (513) 651-2111 

Oklahoma 
Microlithics Inc., Oklahoma City (405) 947-5646 

Texas 
Byte Shop, Richardson (214) 234-5955 
CompuShop, Dallas (214) 234-3412 
Computer Terminal, El Paso (915) 532-1777 
Computerland, Austin (512) 452-5701 
Computers 'n Things, Austin (512) 453-5970 
Interactive Computers, Houston (713) 486-0291 
Interactive Computers. Houston (713) 772-5257 
Micro Computer Shop, Corpus Christi (512) 865-4516 

Washington 
Ye Olde Computer Shoppe. Richland (509) 946-3330 

Ontario, Canada 
The Computer Mart. Toronto (416) 484-9708 



Circle 216 on inquiry card. 



BYTE July 1978 99 



Figure 2: Printer on and off control designed with discrete logic elements. Pressing CONTROL R causes a logic signal to acti- 
vate an external relay in series with the printer power line. Pressing CONTROL T resets this circuit and turns the printer off 



KEY-PRESSED 
STROBE 



ASCII INPUT 
FROM KEYBOARD 



CONTROL R IS 
PRINTER ON 
HEXADECIMAL 12 

CONTROL T IS 
PRINTER OFF 
HEXADECIMAL 14 




1 ^ OUTPUT SIGNAL 

1 ^ TO RELAY, ETC^ 



PRINTER ON 



KEY-PRESSED 
STROBE 



ASCII INPUT 
CONTROL R 
FROM 
KEYBOARD 
022 OCTAL 



such as a printer, and a CONTROL T to turn 
it off. TPie method reaches a point of dimin- 
ishing returns when more than one device 
is to be controlled, though. 

Another disadvantage of this handwired 
decoding is that it is difficult to change the 
decoded value. I recently received a letter 
from a reader who needed a remote reset 
button. He built a circuit similar to the one 
in figure 1, and it worked fine for the soft- 



I702A 




ALL OTHER OUTPUT 
BITS REMAIN HIGH 
HEXADECIMAL 7F STORED 
AT HEXADECIMAL 
ADDRESS 92 



A7 ADDRESS 
INPUT 



DO- D7 DATA 

OUTPUT 



Figure 3: 7 702A erasable read only memory used as an 8 bit address decoder. 
When CONTROL R Is depressed on the keyboard, the output at D7 goes low 
(or true) for a period equal to that of the key-pressed strobe. This circuit can 
replace up to eight of the circuits shown In figure /. 



ware he was using at the time. But when he 
changed from MaxiBASIC to Zapple BASIC, 
he found that the control code he had 
chosen for reset was necessary for use in the 
BASIC, so out came the soldering iron and 
in went another integrated circuit. Then 
came the expansion of more software from 
other manufacturers, and the circuit had to 
be changed again. His complaint was con- 
cerned not with the method of decoding the 
signal but rather with the difficulty in chang- 
ing its particular address. 

I, of course, wanted to have a hardware 
reset and peripheral device controller. I 
could build a combination of the circuits in 
figures 1 and 2 and hope that the next piece 
of software I get doesn't use one of the con- 
trol codes I used, but a concept this simple 
shouldn't require that much wiring or make 
it that hard to change addresses. 

Since I like the idea of using the key- 
board to control the peripheral devices and 
don't like to solder any more than necessary, 
the best alternative for me is a program- 
mable read only memory board control code 
decoder. 

Consider how a programmable read only 
memory works: a binary code is impressed 
on the address input lines and, in the case of 
the 1702A, an 8 bit binary word stored at 
that location appears at the output. By se- 



100 



July 1978 ©BYTE PuUicallons Inc 











Control 












Keyboard 




Hexadecimal 


Octal 


Parity 


Character 


Equivalent 


Alternate Code Names 


00 


000 


EVEN 


NUL 


@ 


NULL.CTRL SHIFT P.TAPE LEADER 


01 


001 


ODD 


SOH 


A 


START OF HEADER.SOM 


02 


002 


ODD 


STX 


B 


START OF TEXT.EOA 


03 


003 


EVEN 


ETX 


C 


END OF TEXT, EOM 


04 


004 


ODD 


EOT 


D 


END OF TRANSMISSION, END 


05 


005 


EVEN 


ENQ 


E 


ENOUIRY,WRU,WHO ARE YOU 


06 


006 


EVEN 


ACK 


F 


ACKNOWLEDGE,RU,ARE YOU 


07 


007 


ODD 


BEL 


G 


BELL 


08 


010 


ODD 


BS 


H 


BACKSPACE,FEO 


09 


Oil 


EVEN 


HT 


1 


HORIZONTAL TAB.TAB 


OA 


012 


EVEN 


LF 


J 


LINE FEED, NEW LINE,NL 


OB 


013 


ODD 


VT 


K 


VERTICAL TAB,VTAB 


QC 


014 


EVEN 


FF 


L 


FORM FEED.FORM PAGE 


OD 


015 


ODD 


CR 


M 


CARRIAGE RETURN, EOL 


OE 


016 


ODD 


SO 


N 


SHIFT OUT,RED SHIFT 


OF 


017 


EVEN 


SI 





SHIFT IN, BLACK SHIFT 


10 


020 


ODD 


DLE 


P 


DATA LINK ESCAPE, DCO 


11 


021 


EVEN 


DC1 


Q 


XOIM,READER ON 


12 


022 


EVEN 


DC2 


R 


TAPE, PUNCH ON 


13 


023 


ODD 


DC3 


S 


XOFF, READER OFF 


14 


024 


EVEN 


DC4 


T 


TAPE, PUNCH OFF 


15 


025 


ODD 


NAK 


U 


NEGATIVE ACKNOWLEDGE, ERR 


16 


026 


ODD 


SYN 


V 


SYNCHRONOUS IDLE,SYNC 


17 


027 


EVEN 


ETB 


w 


END OF TEXT BUFFER, LEM 


18 


030 


EVEN 


CAN 


X 


CANCEUCANCL 


19 


031 


ODD 


EM 


Y 


END OF MEDIUM 


1A 


032 


ODD 


SUB 


z 


SUBSTITUTE 


IB 


033 


EVEN 


ESC 


[ 


ESCAPE,PREFIX 


1C 


034 


ODD 


FS 


/ 


FILE SEPARATOR 


ID 


035 


EVEN 


GS 


] 


GROUP SEPARATOR 


IE 


036 


EVEN 


RS 


A 


RECORD SEPARATOR 


IF 


037 


ODD 


US 


- 


UNIT SEPARATOR 


Note: To transmit any 


control code, depress 


the CTRL key while pressing the character l<ey 


on the same 1 


ine under 


Keyboard Equivalent. 







Table 1: ASCII code 
control characters. 



of 



lectively storing specific values at designated 
locations in the programmable read only 
memory, a single 1702A can be structured 
to perform the functions of eight separate 
decoders like the one in figure 1. For exam- 
ple, if a CONTROL R code were impressed 
on the address lines of the 1702 A, and hexa- 
decimal 7F (binary 01111111) is stored in 
hexadecimal address 12, the most significant 
output bit will go low whenever this pattern 
appears. All other output lines will remain 
at a high level. The same method can be used 
for eight different ASCII codes. The func- 
tion of the circuit shown in figure 1 can be 
performed by an erasable read only memory 
(EROM) as shown in figure 3. 

To use an EROM for this purpose, first 
choose eight different ASCII codes which 
are available on your keyboard and which 
are not used as software control codes. By 
convention, CONTROL Q, CONTROL R, 
CONTROL S and CONTROL T have been 
set aside to represent Reader On, Punch On, 
Reader Off and Punch Off, respectively. The 
other four control codes could be CON- 
TROL W, X, Y and Z, etc. Table 1 shows the 
ASCII control codes. 

An unprogrammed (erased) EROM has all 
bits set to the 1 state. This is true for the 
1702A, the 2708 and the 2716. Next, 



choose eight control codes and make a list 
such as the one in table 2. 

Store the binary word listed at the respec- 
tive address location equivalent to the ASCII 
code with the eighth bit (the strobe bit) set 
high. For a CONTROL R, a hexadecimal 14 
code, this would become an address of hexa- 
decimal 94. When one of these particular 
keys is pressed, a particular output bit of the 
EROM goes low for the duration of the key- 
pressed strobe. Obviously, if only a short 
pulse is necessary for your control applica- 
tion, no further logic is necessary. In my 
application it is necessary to "hold" the 



Table 2: Hexadecimal 
values to be stored In 
EROM to decode eight 
control codes. 









Hexadecimal 






Hexadecimal 


EROM 


Hexadecimal Value to be 


Keyboard 


Code 




Address* 


Stored in EROM 


CTLO 


11 




91 


7F 


CTLR 


12 




92 


BF 


CTLS 


13 




93 


DF 


CTLT 


14 




94 


EF 


CTLW 


17 




97 


F7 


CTLX 


18 




98 


FB 


CTL Y 


19 




99 


FD 


CTLZ 


1A 




9A 


FE 


Note: All other 


address locations 


should have hex 


adecimal FF (fully erased data) 


stored in them. 










*The EROM address is the 


7 bit ASCII code with the eighth bit set high. 



luly 1978 ©BYTE Publicatians Inc 



101 



state of three devices and pulse two of them. 
This requires latches made from external 
gates to maintain the control output after 
the initiating pulse. One method is to trigger 
an RS flip flop on and off with two separate 
codes. In this way, CONTROL R and CON- 
TROL T can be used to turn the printer on 
and off, respectively. Figure 4 illustrates the 
completed keyboard function decoder utiliz- 
ing a 1702A EROM. It allows latched on and 
off control of three devices and pulsed con- 
trol of two more. I chose a 1702A because 
of its cost advantages: at $3.50 it is more 



appealing than a $12.50 2708; but the 2708 
may be more easily programmed for most 
people (see "Program Your Next EROM in 
BASIC," March 1978 BYTE, page 84). It 
can be used instead of the 1702A with the 
appropriate pin assignment changed. Since 
the 2708 is a 1 K EROM and the 1702A is 
256 bytes, the two extra address lines A9 
and A10 should be grounded on the 2708. If 
you decide to use the method of figure 2 
and not use an EROM to make the circuit of 
figure 4, it will take 14 TTL chips just to 
create the logical equivalent of the EROM. 



KEY PRESSED 
STROBE 



ASCII INPUT 

FROM 

KEYBOARD 



Figure 4: EROM-based 
function decoder circuit 
with ttiree latched and two 
strobed outputs. These 
outputs can be used to 
controi soiid state reiays 
and, in turn, printers and 
other peripherais. 



■12V I > ■ 



► 5v(3> 




m 



Notes: 



RECORDER CONTROL 



PRINTER CONTROL 



AUXILIARY CONTROL 



J V- — 1 r- STROBE 

1 ^ '-' CONTROL Y 

J ^ — I r- STROBE 

I -^ '-' CONTROL Z 



1. The EROM is programmed as per the EROM address and binary value infor- 
mation listed in table 1. All other address locations should be left fully erased 
(hexadecimal FF). 

2. The signal outputs from integrated circuits 7 and 8 can be connected to solid 
state relays, which in turn provide on and off control of the designated periph- 
erals. For an explanation and a design of a solid state relay, see "Tune In and 
Turn On, Part 2," May 1978 BYTE, page 97. 

3. All resistors are 1 /4 W 5% unless otherwise specified. 



Key Pressed 

CONTROL Q 
CONTROL R 
CONTROLS 
CONTROL T 
CONTROL W 
CONTROL X 
CONTROL Y 
CONTROL Z 



Function 

Recorder power on 
Printer power on 
Recorder power off 
Printer power off 
Auxiliary power on 
Auxiliary power off 
Bit 1 low true pulse 
Bit low true pulse 



102 July 1978 e BYTE PuMicitJom Inc 



Table 3: Power wiring tabie for figures 2 
and 4. 



Number 


Type 


+5V 


Gnd 


IC1 


7404 


14 




IC2 


7404 


14 




IC3 


7430 


14 




IC4 


7430 


14 




IC5 


7400 


14 




IC6 


1702A 


see schematic 


IC7 


7400 


14 


7 


IC8 


7400 


14 


7 



Some Final Thoughts 

I guess I don't have to worry about find- 
ing someone to be my peripheral "slave" any 
more. The uses of this remote control sys- 
tem can be extended beyond the ones I've 
outlined; my horizons were limited at the 
time. Once I sit back in that chair with a 
keyboard in my lap, it takes an earthquake 
to move me. 

Do you have any questions, comments or 
ideas for an article? Write to me; I try to 
answer every letter. Please enclose a stamped 
self-addressed envelope. Next month: a 
touch panel digitizer." 



o 



I 



To further improve 
service to our customers we 
have installed a toll-free 
'\ WATS line in our 
Peterborough, New 
Hampshire office.^ 
If you would 
i ke to order a 
subscription to\ 
BYTE, or if 

Toll-free \ ^°"'^'^^\ 

I vril 11^^ ^ question relat-> 

to a BYTE ' 



BYTE'S New 



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Subscriber 
W.A.T.S. Line 



ed 



(800)258-5485 



We thank you and look 
forward to serving you. 

3ULaAiLflJUUL8JUA 



subscription, 

you are invited^ 

to call' 

(800)258-5485 

between 8:30 AM and 

4:30 PM Eastern Time. 

^♦Applies to calls made 

from within the 

continental US 

only. 

\\^ 9178; 



A RAM board for only $289? 
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Our RAM board is S-100 compatible, and it has 
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To order your 16K RAM board or to receive more 
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^%«i 



'iili'silnSM 

trmi 



mlml Oafia Ooo^p 

PO Box 2484, Station A 
Champaign, IL61820 
(217)359-8010 



Circle 45 on inquiry card. 



July l97g@BYTE PuUicitions Inc 103 



IDS 



INTERNATIONAL DATA SYSTEMS, INC. 

400 North Washington Street, Suite 200. Falls Church, Virginia 22046 U.S.A. 
Telephone (703) 536-7373 




88-MODEM: A complete serial I/O port and an Originate/Answer MODEM on an 
SI 00 bus compatible board The 88-MODEM features automatic auto-dialer (not 
software timed), operates at any software selected baud rate between 66 and 600 
baud, has separate 8-pole transmit and receive active filters, and all functions are 
software selected The 88-MODEM provides communication to -58 dbm and is intended 
for use with either a CBS (1001 D) or GBT Data Access Arrangement for connection 
to the telephone system The kit price is S245 00 




88-UFC UNIVERSAL FREOUENCY COUNTER: The 88-UFC is an SI 00 compatible 
frequency and period measurement module. The 88-UFC has four software selected 
inputs Frequency measurement to above 600MHz and period measurement to 1 /10th 
microsecond are standard. The counter provides nine digits of readout and is pnced 
ai $179,00 in kit form 




88-SPM CLOCK MODULE: The 88-SPM provides a time of day clock and an inde- 
pendent realtime clock on one SI 00 compatible module Provisions are included for 
battery backup so the 88-SPM can maintain the time during power-off conditions 
$96 00 kit 

1001D (Type CBT) Data Access Arrangement $125,00 

88-RCB 16 Channel Relay Control Board Kit $179,00 

MCTK Morse Code Trainer/Keyer Kit 2900 

TSM Temperature Sensing Module Kit 24,00 

DAC-8 8-Bit Digital to Analog Converter Kit 1 9,00 
88-TCXO Temperature Compensated Crystal 

Oscillator for 88-UFC 145,00 

88-XTAL Crystal Timebase option tor 8B-SPM 25,00 

TERMS Payment with order shipped prepaid, added for COD, Master Charge accepted 



Continued from page 6 

sages sent and received would be the follow- 
ing little loop: 

var 

hangup : boolean; 
hangup := false; 
repeat 

look at keyboard, send latest Input"] 
jnessages to line and display J 

look at line, send any input] 
messages to display J 

until hangup ; 

(This program fragment is represented in 
PASCAL with the use of italics enclosed in 
square brackets [] to denote functions de- 
scribed verbally but not in detail. Note that 
"hangup" is a dummy variable within the 
context of this fragment as shown.) 

This simple programming model is ap- 
plied at both ends of the communications 
line through the phone network. It might in 
fact be implemented in two totally different 
computer and software systems, say in as- 
sembly language on one party's computer 
and in PASCAL on the other party's com- 
puter. It also has the unfortunate disadvan- 
tage of displaying the incoming message 
from the line mixed with the latest outgoing 
message from the keyboard. 

Walking through the process of establish- 
ing and holding a conversation illustrates 
some fundamental points which apply to 
any computer to computer communications 
method. In this case, much of the work in- 
volved in setting up the conversation, the 
protocol, is accomplished manually. Let's 
look at what a conversation between two 
parties might be like, using X and Y as suit- 
able arbitrary names in this script: 

Phone rings. X picks up the phone. 

X: "Hello, X here." 

Y: "Hi, X. Shall we proceed with the 
communications experiment?" 

Note the implicit protocol: Y assumes X 
Is looking for a computer to computer 
conversation. 

X: "Sure. I'll load my program. Let me 
set my modem in the originate mode." 

Y: "Fine. I'll set my modem in the an- 
swer mode and load my program." 

Note the complementary settings of the 
modem modes. For a full duplex con- 
versation, one end must be in answer 
mode, the other end in originate mode. 
A mode is simply the set of transmis- 
sion and reception frequencies chosen 
for use by the modem from two al- 
ternatives. 

X: "I'm starting my program. How's 
yours doing?" 



104 luly 1978 e BYTE Pul>licaliom Inc 



Circle 185 on inquiry card. 



Y: "Mine is just fine. Do you hear the 

tones from the modem?" 
X: "Yes. Okay, let's try the phones." 
Both parties conclude verbal communica- 
tions by placing their phone handsets 
in the acoustic couplers. A computer 
to computer conversation ensues, 
using data from the keyboards and 
sending data to the displays at each 
end. 

This is perhaps one of the simplest models of 
computer to computer communications over 
a phone line via a modem. But it illustrates a 
couple of important points which are re- 
quired in any system which uses the dialup 
network. 

First, there must be a protocol tying the 
two systems together logically. This protocol 
provides a method of establishing contact. 
Here, I used the conversation as an example 
due to the simplicity of the equipment and 
the model. It could be as complicated as a 
full network protocol like those of ARPA, 
PCNET or CIE Net. The protocol must also 
involve the agreement upon a functional 
model of the software driving the communi- 
cations channel. Here the PASCAL program 
fragment, however it is implemented in de- 
tail, provides the common functional model 
for both ends of the line. The actual details 
of a conversation are independent of the 
protocol used. 

Second, the equipment used at both ends 
must be compatible with respect to modem 
design. Here, I have tacitly assumed a 
modem is available which has one outgoing 
channel and one incoming channel. This 
could be a Bell 103 style modem which is 
one of the most commonly available forms 
on the market, or it could be some haywire 
kluge with nonstandard frequencies which 
are shared by the two parties to the conver- 
sation and nobody else. The choice of "an- 
swer" or "originate" in the context of this 
example is arbitrary; when using such a mo- 
dem with a timesharing computer, the 
choice is not arbitrary. 

Third, the protocol can easily be auto- 
mated to some extent; with proper equip- 
ment and appropriate systems software 
running in your system and your network 
correspondent's system, the entire conversa- 
tion can take place without human interven- 
tion from start to finish. But more on that 
subject a little later. 

The conversation just described, and its 
protocol, are not intended as a serious sug- 
gestion for the use of a typical acoustically 
coupled modem. It represents if anything 
just a costly way to bypass the US Postal 
Service and all its problems and transmission 
delays; but then the same is true of the tele- 



16K RAM 

Fully Assembled, Tested^ 
Burned-in 




.»m\T\ii""'* Fully static 

^'"^""'" Using the TMS 4044 

250 nsec. chips — $425 

Z-80A 4 Mhz. Fast — ^Thls fully assembled and tested 
1 6K board was designed to operate without wait states 
in a 4 Mhz. Z-80A system allowing over-generous time 
for CPU board buffers. 

450 nsec. chips — $375 

For 2 Mhz. Systems — Same circuit as above but 
priced lower because of less expensive memory chips. 
It is fully assembled, burned-ln, tested and guaranteed. 

8K Versions Also Available 

Both boards available fully assembled with sockets 
for all 32 MOS chips but supplied with only 8K of chips. 
8K— 250 nsec— $265. 4K chip set— $95. 8K-450 
nsec. — $235. 4K chip set — $85. 

Fully Static is Best — Both boards use the state-of- 
the-art Texas Instruments TMS 4044 which requires no 
complicated and critical clocks or refresh. The fully 
static memory chip allows a straight-forward, "clean" 
design for the board ensuring DMA compatibility. They 
use a single 8 volt power supply at 1 .7 amps nominal. 

Fully S-100 Bus Compatible — Each 4K addressable 
to any 4K slot and separately protected by DIP switches. 

Commercial Quality Components — First quality 
factory parts, fully socketed, buffered, board masked on 
both sides, silk-screened, gold contacts, bus bars for 
lower noise. 

Guaranteed — Parts and labor guaranteed for one full 
year. You may return undamaged board within ten days 
for a full refund. (Factory orders only — dealer return 
policy may vary). 

C/jec/f your local computer store first 

Factory Orders — You may phone for MC, VISA. 
Cashier's check, MO. speed shipment for mail orders. 
Personal check OK. Shipped prepaid with cross country 
orders sent by air. Shipping — Stock to 72 hours normal. 
We will confirm order and give expected shipping date 
for delays beyond this. Washington residents add 5.4% 
tax. Spec, sheet, schematic, warranty statement sent 
upon request. 

V Seattle Computer Products. Inc. 

^•r^ 16611 111th S.E., Renton, Washington 98055 
(206) 255-0750 



Circle 313 on inquiry card. 



July 1978 3 BYTE Publiuliominc 105 



Computers For Everyone! 
Prices For Everyone! 



PET 2001-8 by Commodore 

• 8K user RAM ( expandable to 32K) 

• 8K BASIC in ROM 

• Built-in video display 

• Built-in keyboard with graphic characters 

• Built-in cassette recorder 

PET 8001-8 C8k BAM) $795. 

1 Blank C-10 casseUe SO. 

"BASIC BASIC" Book 9. 



L reg. $824. 



You pay only 



$795. 



Apple II 16K by Apple Computers 



16Kuser RAM (expandable to 48K) 

6K Integer BASIC In ROM 

2K Monitor m ROM 

Pull ASCII kejfboard 

1 6-oolor graphics ( low resolution 40H x 40V) 

4-color graphics (high resolution 280H x 192V) 

Game Paddles Included 

Includes BASIC software on cassette: 

• leKStartreck program • Color demonstration programs 

• 1 OK Floating poixit BASIC • Breakout video game 
tnterpi^ter 

Yoiir color TV set reqiilred for display 



APPLE n C16K BAM) $1195. 

Merlton cassette recorder 80. 

M&B BP ModTilator 30. 



L ^6- $1305. 



You pay only 



$1195. 



Add $1 0-00 per system for shipping and handling. To quali^ for these 
special package prices, ftill payment must accompany your order. We will 
refund full amount if you wish to cancel before we ship. 

Write or Call 

cemputcf 
cmcrpri/c/" 



P.O. Box 71 

Fayetteville, N.Y. 13066 

Phone C318) 637-6208 Today! 



Operating Hours: 
M-W10-8E.S.T. 
Th-riO-9E.S.T. 

Closed Sot. & Sun. 



phone used without a computer. The inter- 
esting uses are those which tal<e advantage of 
the computer at both ends of the conversa- 
tion. Establishing communications between 
modems will involve a similar phone call 
scenario; but now instead of the toy pro- 
gram, suppose we substitute a more interest- 
ing process. 

For starters, a useful utility already em- 
ployed by many personal computer people 
is that of a file swapping program. Here, in- 
stead of keyboard input, after the communi- 
cations is established and verified in a key- 
board to display mode, one or the other of 
the two parties to the conversation accesses 
a local file on floppy disk and dumps it into 
the floppy disk of his correspondent over 
the phone lines. The file sent might be veri- 
fied by the receiving person by one or more 
methods such as grouping the data into 
blocks with checksums or simply sending 
the message redundantly. 

The content of the file sent by this 
method is arbitrary. The file could be as 
simple as the edited text of a letter, or as 
complicated as the source code of the latest 
version of a computer game which the re- 
ceiving person is to try out, evaluate and 
comment upon. And of course, for the occa- 
sional business user or privacy fanatic, the 
program does not have to send the data di- 
rectly: it could use a prime factors cipher to 
ensure that all the computers in the world 
would never be able to crack the code in 
practical lengths of time given our present 
knowledge of such ciphers and their 
properties. 

But exchanging data files still does not 
exhaust the potential of having a computer 
at both ends of the line. What other activi- 
ties involve participation by people at each 
end of the line? (Remember: we are still 
using simple modems with a manual pro- 
tocol at the start of communications.) A 
computer at each end and a person operating 
the computer sounds like defining character- 
istics of a new class of challenging computer 
games. 

For one degenerate case, let us suppose 
that each player has as his goal to "take 
over" the other player's computer, using a 
commonly defined operating system nucleus 
and a set of rules governing legal moves. The 
result would be a very abstract, possibly 
quite exciting (and possibly quite dull) 2 
processor remote version of the classic called 
core war. [Core war is a game surrepti- 
tiously played by systems programmers on 
large installations, where a player's goal in 
each fixed time slice of real time is to propa- 
gate his program elsewhere in memory, while 
doing as much "damage" (read: clearing to 
zero) as possible at random places in the 



106 luly 1978 e BYTE PuWicilions Inc 



Circle 70 on inquiry card. 



hopes of causing the opponent's program to 
blow up.] The game of core war is rarely 
mentioned with more than a whisper, and 
thus tends to be lost amid the din of easier 
and less abstract games such as Star Trek, 
Adventure or Dungeons and Dragons. But, 
just as a 2 computer version of a classic is 
possible, these contemporary games might 
well be adapted to a 2 sided mode employ- 
ing two computers and two teams of players. 

Games border on the world of simula- 
tions, and simulations border on the world 
of games. The use of two local processors 
across the phone lines (or in the same room 
sans modems) has much potential. Suppose 
each computer is running a simulation of a 
plane in flight. A natural variation would be 
to loosely couple the state variables between 
the similar programs across the link, so that 
the two "pilots" could attempt formation 
flying and maneuvers. The key software 
which is needed is of course a simulation 
program with direct memory outputs to a 
display on each computer, and the ability to 
keep track of the "other guy" from the 
point of view of the local simulation. For 
most one player versus the computer games, 
the random number sources of data typically 
used could be replaced by parameters re- 
ceived across the communications line from 
the second computer. At 300 bps (30 char- 
acters per second, roughly) the potential for 
some 2 party interaction is definitely pres- 
ent, relying upon local simulations in each 
computer for most of the actions observed 
on each screen. 

But enough of this blue sky. How much 
does the equipment cost? All of these 
suggestions could be implemented using a 
typical personal computer which has a spare 
serial lO port with RS-232 levels (the more 
floppy disk drives the better of course, with 
zero as the minimum acceptable number). 
The cost for the modem, based on two 
advertisements in the May 1978 issue of this 
magazine, would be either $139 or $129 
depending upon whose modem you buy. 
The basics require no particular attention to 
the phone line itself, other than making sure 
you have a standard handset which fits the 
acoustic coupler. And of course, having 
made the investment you also get access to 
the local time sharing service, which may 
have such juicy tidbits as cross assemblers 
and compilers which are not yet up and 
running on your own system. But this is 
merely a taste of the possibilities of tele- 
communications: even more function can 
be had at a slightly higher expense through 
the use of modems which feature automatic 
dialing, automatic answering and telephone 
company compatible "data access arrange- 
ment" (DAA) features. 




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6304 Yucca/Hollywood, CA 90028 
(213) 462-5652 




Circle 320 on inquiry card. 



July 1978® BYTE Publications Inc 



107 



Circle 311 on inquiry card. 



JULY 
FIREWORKS 




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Tarbell Cassette Interface Kit 

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Trace Electronics 32K Static 

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North Star Floppy Disk Kit 

MDS-A 

with Power Supply Cabinet 

and 3 Extra Diskettes 790^ 

All T.D.L Systems 30% Discount 

T.D.L D-32 Memory Board - Assembled 
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Above Prices Include Cash Discounts. 

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Don Lancaster's ingenius design provides software 
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• Over 2K cm-screen characters with only 

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• Variety of line/character formats including 
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• User selectable line lengths 



TELL ME MORE! ( ) send instruction manual for the TVT-6 Kit 
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DEPT. 7-B, 1020W.WILSHIREBLVD.. OKLAHOMA CITY. OK 73116 



Automatic Communications: 

A^ computers + N People + Auto Answer 
+ Auto Dial + DAA 

The protocols appropriate for an acousti- 
cally coupled modem are heavily biased by 
the need for manual operations. Just as the 
audio cassette recorder is the poor second 
cousin of the floppy disk as a mass storage 
medium, the acoustically coupled modem 
works for telecommunications but has many 
fewer features of merit than the more 
expensive modem options. 

The first extension to consider is that of a 
form of the modem which is wired perma- 
nently to the phone company's network via 
an appropriately approved data access 
arrangement or DAA. Given this extension 
alone, there would apparently be no great 
improvement in function relative to the 
simple acoustic modem. 

Thus we must consider the second 
extension, use of an auto answer option 
through the data access arrangement. Here, 
with appropriate software, your computer 
gets a signal from the interface which tells it 
when someone is calling. The computer can 
then reply with a signal which "lifts the 
phone off the hook" by changing appro- 
priate electrical levels in the interface which 
simulate that normally manual action. The 
computer can then proceed to verify that 
there is indeed a modem on the other end 
and commence its automated version of that 
conversation between X and Y given a little 
earlier. For thorough description of how 
such protocols work, consult any text book 
on systems software for timesharing sys- 
tems: this model is used by your friendly 
timesharing service to receive calls from its 
users with ordinary modems at the other 
end. 

The third of these three extensions of the 
basic model is the auto dial function. Here 
the intent is to allow your computer to place 
the call automatically, an event which 
implicitly assumes the number being dialed 
can receive such calls unless the modem is 
disconnected after the call is made. 

This more general function can be had at 
reasonable prices. The board used by Ward 
Christensen and Randy Suess costs about 
$300 assembled and tested, plugging into 
an S-100 bus slot. Another brand, also 
assembled and tested, but complete with a 
Bell approved data access arrangement 
module, runs about $500 and also plugs into 
an S-100 bus slot. (The difference between 
buying your own data access arrangement 
module or using a phone company version is 
one of paying monthly installments forever 
or paying a lump sum of about $100 to 
$150 once.) 



108 |ul> >9;6^BYU rublicitioniinc 



Circle 298 on inquiry card. 



Circle 136 on inquiry card. 



With the economics of the auto dial and 
auto answer versions and data access arrange- 
ment settled, what are the possibilities which 
may be fulfilled? First, there is the matter of 
regular correspondence with a close friend 
on the other side of the continent. If you 
communicate via the simple model of the 
unautomated link, your prime time for 
originating a call may be different from the 
hours of prime functioning as a human 
being. The phone company rates are much 
lower in the wee hours of the morning. So, 
let your automated computer servant sit up 
late and take advantage of the cheap rates to 
telephone your correspondent's computer, 
send the mail you left for him or her and of 
course receive the mail left for you. More 
than one correspondent? Simply keep a list 
of phone numbers associated with the 
names, and call all of the ones which have 
been left messages on a disk file or in mem- 
ory. Don't care to waste phone charges? 
Well, use the auto answer feature to wait for 
your correspondent's calls. (This concept of 
using the auto answer and auto dial features 
to implement Telemail service is one of the 
pet projects of Ken Bowles at the University 
of California at San Diego. We can expect to 
see a protocol established from that source, 
written in PASCAL of course, which will be 
widely available for a nominal charge.) 

Let's extend the model a bit to the world 
of games so often frequented by the per- 
sonal computer user. But now, consider the 
N party game, a sort of computerized 
version of Dungeons and Dragons viewed as 
a prototype of the N player simulation 
game. Now, the phone network and dialup 
features can be used to some advantage: 
instead of one week's long conversation on 
a party line (the brute force approach), each 
player node in the game has a computer with 
a local model of the game plus interaction 
models which involve dialing up other 
players in the game for information or to 
send game messages which affect the other 
players. To be less than prohibitive in line 
costs, it would have to be done locally 
within a "free" dialing zone of your local 
exchange. It is a challenging problem to even 
think about defining such a game, let alone 
playing it. It is a suggestion which is quite 
within the capabilities of a dedicated group 
of N enthusiastic participants. Who will be 
the first to define and implement such a 
discipline? 

And then, of course, there is the less 
esoteric but quite useful concept of the local 
computer club bulletin board, as prototyped 
by Ward Christensen and Randy Suess. Here, 
both the auto answer and the auto dial 
modes can be used to advantage. The auto 
answer mode is of course currently being 



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The Best SELECTRIC II* Printer Going 
for ANY Computer! 



SEI,FCTRA-TERM is a liraiid 
new IBM Selectric II* typewriter 
which has been fully converted 
for direct connection to your 
computer. A special typing ele- 
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upper/lower case alphanumerics. 
You also have backspace, tab. in- 
dex and bell— all under computer 
control. 

SELECTRA-TERM can also be 
used as a standard typewriter. It 
has been approved for computer 
use and comes with the IBM war- 
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typewriter portion. MCD provides 
*Reg. trademark of IBM Corp. 

Circle 226 on inquiry card. 



their own factory warranty on the 
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Complete electronics package, 
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Telephone (714) 992-2270 

luJy 19786BVIt Publicalions Inc 109 



Circle 1 13 on inquiry card. 




ECHOlab 



A card guide compatible with the Altain-' 

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Speed nuts replace self-tapping screws for 

ease of installation. 

These guides also feature extra-rugged black 

ABS plastic construction. 

10 S1.50ea. 

25 S1.35ea. 

100 S1.20ea. 

1000 Sl.OOca. 

Availability-stock to 30 days. Please en- 
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ECHOlab, Inc. 

213 Middlesex Turnpike 

Burlington, MA 01 803 (617)273-1512 



employed in the interactive message center 
concept: users can call in from anywhere 
and leave messages which are either broad- 
cast, or specific to particular users. The club 
can also prepare a file which is sent to every 
active user upon logging into the system. 

The concepts of auto dialing and autc 
answering can also be applied to personal 
use independent of the use of the modem 
if provision is made to manually switch from 
modem data to voice data. The auto answer 
feature is of course typically used in a 
standard telephone answering machine, but 
by having your computer answer the line 
and listen with one of several voice response 
boards on the market, you might be able to 
call up your house and have various options 
such as lights, radios or sprinklers change 
state in response to voice command. If the 
voice recognition method of remote control 
does not work then consider using a touch 
tone telephone to send a coded pattern of 
numbers which are detected by another 
special demodulator after the phone is 
answered. 

Auto dialing coupled with the usual voice 
mode enables you to build a file of fre- 
quently called numbers, a "little brown disk" 
instead of a little black book. These numbers 
could then have symbolic names like 
"FIRE," "MOTHER," "SUZY," "JUDY," 










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110 |uly 1978 © BYTE PuMicatians Inc 



Circle 35 on inquiry card. 



Circle 61 on inquiry card. 



Circle 101 on inquiry card. 



etc. When a phone conversation is desired, 
dialing could be done symbolically by 
selecting a name with one character referring 
to a menu list on your display. Of course 
there are certain things one would not want 
to do with an auto dial feature, such as 
create intrusive automatically dialed junk 
phone calls. 

Summarizing the State of the Art. . . 

Computer to computer communications 
via the dialup phone network are a very real 
possibility for the personal user. The com- 
munications can be as simple and inexpen- 
sive to implement as an acoustic coupler on 
an ordinary telephone, or slightly more 
elaborate (but still less than $500 for an 
S-100 bus computer) with automatic answer- 
ing and dialing features. However you 
implement your link to the outside world 
from a personal computer, the applications 
of the system expand considerably." 



How Much Is That Turtle in the Window? 

As noted with a photograph and some 
background information on page 6 of the 
March 1978 BYTE, personal computer 
users will soon be able to add an abso- 
lutely fascinating new peripheral: an 
electromechanical "turtle." Recent word 
from Cambridge is that the Terrapirr 
turtle was scheduled for a mid May press 
conference announcement by Terrapin 
Inc, 33 Edinborough St, 6th Floor, 
Boston MA 02111. (This note was 
written April 24 1978, following a phone 
conversation with David McClees of 
Terrapin.) 

Using simple programming concepts in 
versions of the LOGO language, it is 
possible to teach young children many of 
the concepts of computer science using 
the mechanism of the turtle to emphasize 
points. Also quite possible with such a 
mobile robot appendage are various other 
applications from delighting friends at an 
adult or child's party to implementing the 
world's least expensive plotter output 
using the tail dragging capability of the 
turtle's solenoid controlled pen. Sensors 
on this inexpensive robot are four micro- 
switches which can determine one of 
eight possible directions when the unit 
runs into an object. 

How much for that "turtle in the 
window" at your local pet store? While 
final prices have not yet been set, the kit 
version is expected to be about $300. To 
be complete, Terrapin Inc will also sell an 
assembled version for $500 or so." 



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Mail to: Information Unlimited (authoriied distributor) 
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n Model NS 3 for North Star BASIC (requires 24K RAM). $75.00 

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[J More information (I'm running disc BASIC 




computer) 
A CREATION OF 

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BOX 14694 SAN FRANCISCO 941 14 



Circle 73 on inquiry card. 



July 1978 e BYTE PuWkaliom Inc 111 



Lsngusges 
Fopuff) 



Pat Fitzgerald 

Winchmore Irrigation Research Station 

Private Bag 

Ashburton NEW ZEALAND 



BASIC to Assembly Language Linkage 



Listing 1: PDP-ll assembly language listing of program to output a quo- 
tation mark. 





177564 


TPS =177564 




177566 


TPB =177566 




000050 


.=50 


000050 


037426 


-WORD SEXF 




037426 


.=37426 


037426 


105767 SEXF: TSTB TPS 




140132 




037432 


100375 


BPL SEXF 


037434 


012767 
000042 
140124 


MOV #042, TPB 


037442 


000167 
140404 


JMP 52 




000052 


.END 52 



; teleprinter status 
; teleprinter buffer 
;link between BASIC and 
;external function 
; start address of 
; external function 
; is printer ready? 

; if not branch 

;move ASCII code for quotation 

;mark to buffer and print 
.•return to BASIC 



Listing 2: Driver program for the assembly language program in listing 1. 

10 PRINT "IN BASIC THE QUOTATION MARK ( " ; 

2 LET T = EXF(l) 

30 PRINT") IS A DELIMITER" 



Listing 3: Sample run of the BASIC program of listing 2. This is one simple 
solution to the problem of printing a quotation mark in a BASIC inter- 
preter, lacking appropriate escape mechanisms. 

IN BASIC THE QUOTATION MARK (") IS A DELIMITER 



Frequently one needs to use a BASIC 
interpreter to do things it was never designed 
to do. Getting around the problem can 
require a great deal of ingenuity. A case in 
point is David Chapman's article, "All This 
Just to Print a Quotation Mark?", in May 
1977 BYTE. 

Several versions of BASIC allow assembly 
language programs to be added to the BASIC 
interpreter; these programs are linked to 
BASIC at load time and usually cannot be 
deleted without reloading BASIC. Using this 
technique provides a very simple method of 
getting around the problem described by 
David Chapman. The assembly language 
listing is given in listing 1 and the BASIC 
language program is given in listing 2. A run 
of the program is in listing 3. It appears that 
a relatively simple solution to the problem 
has been found. 

The version of BASIC I use is single 
user Digital Equipment Corporation's BASIC 
V008A for the PDP-ll series of mini- 
computers. This BASIC allows the user to 
call the assembly language program by use 
of an EXF function. Obviously in other 



ivhy the last mllla§ is the best 




It has the lates 
(and prospective 
Co. computer pro 
company-control 1 
new product info 
bits about items 
before the offic 
by Heath Co. Bu 
than that--BUSS 



t news for users on news of compatible hardware & 

users) of Heath software from other vendors. H8 

ducts. It isn't and Hll users may save enough on 

ed--BUSS can get these products to pay for a BUSS 

rmation and tid- subscription several times over, 

being developed And users of the ET-3400 Trainer 

ial announcement aren't left out either, 

t BUSS does more The first issue of BUSS came out 

also lets you in more than a year ago in April of 



1977. Every issue goes by first 
class mail and almost all orders 
for new subscriptions are filled 
within two days. Back issues go 
fast, but most of those for 1978 
are still available. BUSS keeps 
getting better. So send for it: 

12 Issues For $ 5.80 



The Independent Newsletter of Heath Co, Computers 325 Pennsylvania Avenue, S.E, Washington, DC 20003 



112 



luly 1978 ® BYTE Publicjtionj Inc 



Circle 36 on inquiry card. 



versions of BASIC the calling procedure 
will be different. The EXF function call 
can be used as an expression or as an ele- 
ment of an expression anywhere that an 
expression is legal in BASIC syntax. 

The assembly language program is called 
by use of the EXF function. The argument 
for the quotation mark program is a dummy 
one and any number would suffice. However 
this is a trivial use of the power of the link- 
ing method. More useful programs can be 
written to allow BASIC to be used in a 
variety of applications from real time con- 
trol of instruments to reading data from 
cassette transports. It can also be used to 
add powerful functions to increase the 
number crunching ability of BASIC. In 
short the uses of this tool are only limited 
by the user's imagination. 

One particular use we can make of the 
assembly linkage is a program to retain a 
BASIC program in the machine when the 
power is turned off. On the PDP-11 series 
when BASIC is restarted, information 
necessary to recall the user program is 
lost from two of the volatile registers 



(although the main core memory returns its 
information). However, use of the assembly 
language program shown in listing 4 allows 
the contents of these registers to be saved on 
power down and restored at power up. 

To use this program when you have 
temporarily finished with the BASIC pro- 



Listing 4: A nontrivial use of BASIC to assembly language linkages. This 
PDP-11 assembly program saves the PDP-11 's registers and restores them 
so that the program may be used after a restart occurs. 





000001 




R1 = %1 




;define registers to 




000005 




R5=%5 




;be saved 




000006 




SP=%6 




;register 6 to be stack 




000050 




.=50 








037406 




.=37406 




037406 


010146 


START 


.MOV 


Rl,- (SP) 


;save Rl and R5 


037410 


010546 




MOV 


R5,-(SP) 


;on stack 


037412 


010667 
000016 




MOV 


SP,SAVE 


;save stack 


037416 


000000 




HALT 




;EXIT AND RE-ENTRY POINT 


037420 


016706 
000010 


RSTRT 


:MOV 


SAVE,SP 


.-restore stack and 


037424 


012605 




MOV 


(SP)+,R5 


; registers 1 and 5 


037426 


012601 




MOV 


(SP) +,R1 




037430 


000167 
140416 




J MP 


52 


;back to BASIC 


037434 


000000 


SAVE: 


.WORE 









000052 




.END 


52 





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3455 Conner St., Bronx, N.Y. 10475 (212) 994-6600 / Telex 125091 



Circle 289 on inquiry card. 



luly 1978 <&J BYTE Publications Inc 113 



gram, you type "Print EXF (N)" where N 
is an arbitrary number. When you wish 
to reuse the program, you start at address 
037420 rather than the conventional 
000000 which would destroy the user pro- 
gram. The machine responds by typing the 
number N. In this version of BASIC the 
linkage between the interpreter and the 
assembly language program is maintained 
through location 50; this address must 
contain the start address of the assembler 
language program. Return to BASIC is 
achieved by a jump to location 52. Several 
arguments can be used in the EXF function, 
but it is the user's responsibility to evaluate 
each argument after the first. By this tech- 
nique an assembly program with several 
entry points can be called up from a BASIC 
program to do a multitude of tasks not 
provided for in the BASIC language. 

Of course this requires that the pro- 
grammer learn the assembly language. 
Fortunately for the PDP-1 1 user an excellent 
introductory manual has been provided by 
R W Southern (see references). 

Moral 

Try using assembly language programs 
before attempting complex contortions 
within BASIC." 



REFERENCES 

Chapman, David, "All This Just to Print a Quota- 
tion Mark?", May 1977 BYTE, page 132. 

Southern, R W, PDP-11 Programming Fur)da- 
mentals, Algonquinote 12, Algonquin College 
Bookstore, Ontario CANADA, 1972. 



Languages Forum is a 
feature wliich is intended as an 
interactive dialog about tlie 
design and implementation of 
languages for personal com- 
puting. Statements and 
opinions submitted to tfiis 
forum can be on any subject 
relevant to its purpose of 
fostering discussion and com- 
munication among B YTE 
readers on the subject of lan- 
guages. We ask that all corres- 
pondents supply their full 
names and addresses to be 
printed with their commen- 
taries. We also ask that corres- 
pondents supply their tele- 
phone numbers, which will be 
printed unless we are expli- 
citly asked to omit them. 



BASIC is BASIC is ... 



And BASIC does what it should. But if you're ready to step up 
from Beginner's All-purpose Symbolic /nstruction Code, look 
at OPUS, the high-level 8080/Z80 language from A.S.I. .. . roots 
in BASIC, but designed for business applications. OPUS gives 
you the capabilities you need, like extended precision, string 
handling, and easy formatting. OPUS/TWO takes up where 
OPUS/ONE leaves off, allowing subroutines, overlays, and 
extended disc file management. 

But we didn't stop there. OPUS programs and data are 
directly upward-compatible, all the way up through TEMPOS, 
A.S.I. 's multi-user, multi-tasking operating system. 

Ask your dealer, or contact A.S.I. We'd like to tell you more. 



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S.O.S $385.00 



OPUS/TWO $195.00 

TEMPOS $785.00 




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Add $1.50 per manual (set) for shipping/handling in U.S. 



114 July 1978 ©BYTE PuMicilionsInc 



Circle 4 on inquiry card. 






Fooling 

with the Stack Pointer 



I think Dr Borrmann ("Relocatability and 
the Long Branch," page 26, October 1977 
BYTE) used the right word when he said he 
was "fooling with the stack pointer." Using 
the stack pointer as a general data pointer is 
bad programming practice; when the system 
uses NMI interrupts for real time clock main- 
tenance it is simply intolerable. In this case 
it is not even particularly necessary: the 
same two subroutines can be implemented 
in a stack-safe way for only eight more 
bytes, as follows: 



Tom Pittman 

POB 23189 

San Jose CA 95153 



Label Op Code 


Operand 


Commentary 


LONGBS STX 


XSTOR 


[save X for later] 


DES 




make room for copy of return 


DES 






TSX 




point to it in X 


PSHA 




save A on stack 


LDAA 


3,X 


low byte of return address 


STAA 


1,X 




ADDA 


#2 


point to actual return 


STAA 


3,X 




LDAA 


2,X 


high byte of return 


STAA 


o,x 




ADCA 


#0 


finish add 


STAA 


2,X 




BRA 


BPUSH 


skip over start of LONGBR 


LONGBR STX 


XSTOR 




PSHA 






BPUSH PSHB 




save b on stack 


TSX 




point to top of stack in X 


LDAA 


3,X 


get address of offset . . . 


LDAB 


2,X 


. . . into A&B 


LDX 


2,X 


also into X, 


ADDA 


1,X 


so to add offset 


ADCB 


o,x 


to its address 


TSX 




get back to stack 


STAA 


3,X 


put sum there 


STAB 


2,X 




PULB 




restore saved A&B 


PULA 






LDX 


XSTOR 


[restore old X] 


RET 




[go to address] 



Dr Borrman illustrated a very good idea 
with a poor program. However, it was a good 
article, bringing to people's attention the 
fact that the 6800 alone of all popular 
processors is capable of self-relocatable code. 
Something that Dr Borrmann perhaps did 
not notice is that the subroutine LONGBS 
(and its chain of BRA stepping stones) is 
superfluous. At least where the subroutines 



now 



sour 

with 

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arbitrary length key{s). Ascending or 
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California purchasers add Sales Tax 
Pre-paid only. Immediate delivery 

Dralvr inquinrs invitrii 

*CP/M IS a trademark of Digital Research 




Circle 308 on inquiry card. 



BYTE )uly 1978 115 





BSR 


LINKn 




BRA 


EXITn 


LINKn 


BSR 


LONGBR 




FDB 


SUBR-* 


EXITn 







are to be included in the program, it is 
probably more economical to do the sub- 
routine calls this way: 



[Instead of JSR LONGBS] 
[jump over linkage] 
[or JSR if LONGBR Is in monitor] 
[relative address of subroutine] 



There is also the technique of using the 
indexed addressing mode with JMP or JSR 
when X is not needed in the call itself. Once 
in the program you compute the address of 
the first of a dense block of subroutines. 
Then each time you need one, the following 
linkage is used (notice that LONGBR is not 
needed): 



LDX 
JSR 



AFIRST =address of first subroutine 

SUB-FIRST, X 



The easiest way to compute the address 
of FIRST is to jump to a BSR just before it 
as shown next: 





BRA 


INIT 


(part of initialization) 


SAVEIT 


PULA 




get high byte 




STAA 


AFIRST 


save it in RAIVl 




PULA 




now low byte 




STAA 


AFIRST+1 


(continue with main program) 


INIT 


BSR 


SAVEIT 


push address onto stack 


FIRST 






(first subroutine) 



If every subroutine knows its stack depth, 
you can leave the return address generated at 
INIT on the stack, then use the following 
calling sequence: 



TSX 
LDX 
JSR 



depth, X 
SUBR-FIRST 



point to stack 

get saved address of FIRST 

X 



Of course these will not work if you need 
the index register to pass an argument to the 
subroutine." 



More On Varistors: 

A Supplier of Some Note 

Comments 



William G Morris 

General Electric Research 

and Development 

POB8 

Schenectady NY 12301 



I don't know which brand of varistor 
Stephen Sorger of W N Phillips Inc (Letters, 
April 1978 BYTE) was using when he 
experienced "aging," thermal "runaway," 
and a "fire hazard," but it certainly was not 
a General Electric GE-MOV"^ varistor. As 
a typical example, the V130LA10 GE-MOV 
varistor will run at full rating to 85 °C 
ambient, which is 15°C greater than Intel 
specifies as maximum temperature for the 
8080. This varistor also exhibits an observed 
failure rate of less than 0.2% per 1000 hours 
during accelerated testing at 100 °C ambient. 

The reader should be reminded that tran- 
sient suppression is essential to reliable 
operation of microprocessor systems, par- 
ticularly in industrial environments, but also 
in hobby applications. Varistors continue to 
represent the most cost effective method of 
achieving transient suppression. 

The V130LA10 GE-MOV varistor, which 
can be used directly on 110 VAC lines, is 
available for $1 to $2 from most industrial 
electronics suppliers. Additional information 
is available from General Electric Company, 
Electronics Park, Syracuse NY 13201." 



-r^'Wi 



$95 Stand Alone Video Terminal 



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Call or write today. MC/VISA accepted 

I XITEX CORP. P.O. Box #20887 

I Dallas, Texas, 75220 • Phone (214) 386-3859 
/ Overseas orders and dealer inquiries welcome 



116 luly 1978 © BYTE PuUicUMm Inc 



Circle 400 on inquiry card. 



Beck fieviews 



Instant Freeze-Dried Computer 

Programming in BASIC 

by Jerald R Brown 

Dymax, POB310, Menio Park CA 94025 

$6.95 



How quickly the personal computer 
owner trades the student's notebook for 
the teacher's chalk. Says the friend, "Neat, 
you got a computer. How do you get it to 
do X or Y?" Or you modestly back yourself 
into a corner; "Programming isn't hard. I 
could teach you BASIC in a few hours." 
In my case it was a deal with my neighbor's 
recent high school graduate to teach him 
programming in return for his doing some 
of my more routine programming chores. 
But however you got the teaching job. 
Instant Freeze-Dried Computer Program- 
ming in BASIC is in my opinion an inter- 
esting, involving and entertaining text you 
can use to ease the teaching task. 

The book resembles a half inch thick 
collection of BASIC oriented flashes that 
somehow escaped from the pages of Ripley's 
Believe It or Not. We see the scene of the 
keyboard LET fading into the sunset beyond 
the hills, captioned by "And so, in the name 
of Efficiency and Ease, the LET was 
banished forever from Statementland. . . ." 
Throughout each page the student is ex- 
horted to either read the explanatory text, 
or, more often, "do it": the signal for you to 
actually type out one of the hundreds of 
brief examples on your waiting terminal. 
The layout is designed to be both a text 
and a practical workbook. For example, 
immediately after you learn to loop with the 
GOTO statement, half inch type warns you 
to "WAIT! STOP! HALT! CEASE! 
DESIST!" before running, so the saving 
properties of the Control-Ccan be explained 
to keep you from the terror of the infinite 
loop. 

The examples are so clear that not even a 
computer could complain of ambiguities. 
The actual keys punched are pictured using 
the standard key markings of the ASR-33 
Teletype. The printed listing for each 
example explains why you typed this and 
why the computer typed that. 

Besides being an excellent teaching text, 
the book has the two necessities that make 
it a handy manual to keep forever, plus 
several bonuses. The necessities are a set of 
concise summary boxes at appropriate spots 
throughout the text gaudily surrounded by 
polka dots; and a good index that not only 



tells you where the concept is taught, but 
the precise location of the summary box. 
The bonuses are the examples cnosen by the 
author: a broad set of games, pictures, 
string techniques and useful business pro- 
grams, all indexed and ready to run. 

The dialect of the BASIC taught is both a 
strength and a weakness of the text. Altair 
8 K BASIC, revision 3.2 (essentially the 
same as DEC BASIC Plus), is that ubiquitous 
version that started so many of us hackers 
off in BASIC and served us so well. But 
revision 4.0 is now out, and, especially in its 
extended version, it far surpasses 3.2 8 K 
BASIC in flexibility and power. But of 
course, the further you go from standard 
BASIC the more machine dependent you 
become. For the beginner, or those writing 
for a variety of interpreters. Brown's choice 
was a wise one. 

All said. Instant Freeze-Dried Computer 
Programming in BASIC is the most painless 
and involving text for that language yet on 
the market. 



Jay P Lucas 

3409 Saylor PI 

Alexandria VA 22304 a 



Address Correction 

David Clapp, who re- 
viewed Z-80 Programming 
Manual by IVIOSTEK (June 
1978 BYTE, page 118) has 
changed his address to: 
FOB 501, Streetsboro OH 
44240.* 




A 






SOFTWARE 
SYSTEMS SPECIALISTS 



Growth corporation has immediate openings AT 
ALL LEVELS for candidates with a BS or MS in 
Engineering/Science and a bacl<ground in the follow- 
ing areas: 

■ Microprocessors ■ Minicomputers 

■ Real Time Systems ■ Operating Systems 

■ Event-Driven Applications ■ Diagnostic Programming 

■ 8080 Assembler, PLM 

TECHNICON is the industry leader in the manu- 
facture of State-of-the-Art automated laboratory 
instruments. Located in suburban NY, we provide 
a professional working environment, along with 
competitive salaries and a full range of company- 
paid benefits. Send resume including salary history 
in confidence to: 

Manager, Technical Staffing 

Tomorrow's Technology Today 



Iliil lechnicon 
IIIIH Tarrytown, N.Y. 10591 



An Equal Opportunity Employer M/F 



Circle 373 on inquiry card. 



)ulv 1978 © BYTE Publications Inc 117 



eVTE's Ells 



Portia Isaacson to Edit New Bool< Series 

Announcements in BYTE's Bits are 
usually confined to products and services 
rather than details of who is doing what 
in the personal computing industry. We 
could never hope to find room to print 
all the people oriented press releases 
that come our way every month. Be- 
cause of the contributions she has made 
to personal computing, however, we are 
making an exception here to report 
that Portia Isaacson has now joined 
book publisher Prentice-Hall as series 
editor and advisor for the firm's new 
Personal Computing Book Series. 

Dr Isaacson is currently chairperson 
of the ACM Special Interest Group in 
Personal Computing, editor of a monthly 
"Personal Computing" column in Data- 
mation, acting president of the Com- 
puter Retailers Association, an Elec- 
tronic Data System fellow, and co- 
owner of the Micro Store. Named 
as an honorary fellow of the Asso- 



ciation of Computer Programmers and 
Analysts in 1977, she also chaired 
the 1977 National Computer Confer- 
ence. Dr Isaacson has been associated 
with Textron, Lockheed Electronics, 
and Xerox Corporation and is a former 
university professor. She will author 
the first book in the Personal Computing 
Series, 777e Microcomputer in Business.* 



Heard on a BOMB Card 

"If this feedback helps you why is 
this card not postage paid? 1 really do 
not know why 1 put a stamp on this every 
month. You really do not want this card 
back, do you?" 

Why does anyone write a letter to the 
editor? It costs a minimum of $.13 and 
has no guaranteed or measurable result 
for the sender. Formalized rating feed- 
back is quite adequately provided by 
those readers who are opinionated 
enough to return a filled out BOMB 
card. If we received as much as 10% of 
the 135,000 or so cards mailed with the 
May 1978 BYTE, the analysis would re- 
quire a nearly full-time person. By pro- 
viding the filter of requiring a person to 
back his or her opinion with a stamp, the 
numbers are kept within manageable 
limits. . .CH" 




At the suggestion of a reader, this 
emergency equipment now hangs on a 
certain editor's wall at BYTE. The hexa- 
decimal abacus was created by Blaise 
Liffick, and the now obsolete scientific 
and engineering calculator at one time 
was the primary computer of yours 
truly. . .CH" 



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Convenient plug-in card, fully burned-in, tested and guaranteed by one of 
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See your dealer, or contact us for complete information. 

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NMOS static RAM 



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eVTPs Bugs 



DeMorgan Gets Half-Bombed 

An error appeared in one of the defi- 
nitions of DeMorgan's two laws in Dan 
Bunce's "Some Musings On Boolean 
Algebra" (February 1978 BYTE, page 
26, second paragraph). The last sentence 
of the paragraph should read: ^igure_3a 
also gives us the other law, p \/ q = 
p A Q'" Thanks go to Steve Shade, 
Lehigh University, Bethlehem PA 18015, 
for spotting this error." 



Microbot Bug 

A minor bug appeared in listing 1 of 
John Webster's "Robot Simulation on 
Microcomputers" (April 1978 BYTE, 
page 1 36). The assembler code at address 
0017 should read: "LXI B, 0A040H" 
instead of "LXI B, 0A004H." The hex 
code listing is correct as it stands." 



Correction 

The address for Pickles and Trout on 
page 51 of Dan Fylstra's "The Radio 
Shack TRS-80: An Owner's Report" 
(April 1978 BYTE, page 49) should 
read: Pickles and Trout, POB 1206, 
Goleta CA 93017, (805) 967-9563. Our 
apologies to Messrs Pickles and Trout." 



118 July 1978 <D BYTE Publicilions Inc 



Circle 132 on inquiry card. 



Ppogpsmming 



iHEADER PROGRAM TO HOI^E BASIC OVER NORTH STAR DOS 



Ouickies 



Beating North Star — 
MITS Incompatibility 



Alan R Miller 
New Mexico Tech 
Sorocco NM 87801 



If you have a North Star floppy disk and 
you want to use it to load MITS extended 
BASIC, there may be a slight problem. The 
North Star disk operating system requires 
2.5 K bytes of memory starting at hexadeci- 
mal address 2000. MITS extended BASIC 
also uses this same area. The solution is sim- 
ple: load BASIC in the old way (cassette or 
paper tape), but don't start it up. Next, load 
the 23 byte automove program in listing 1 
at hexadecimal 4000. Use it to relocate 
BASIC at hexadecimal 4020. Jump to hexa- 
decimal E900 and reload the disk operating 
system. Finally save the combination auto- 
move and BASIC (hexadecimal 4000 to 
7FFF for version 4.0; hexadecimal 4000 to 
6FFF for earlier versions) on the North Star 
disk with file name MBASIC. 

When you want to load MITS BASIC 
from disk, type GO MBASIC and the disk 
will copy BASIC into memory above the 
disk operating system and jump to the auto- 
load routine. This routine will in turn copy 
BASIC into its proper location, then jump to 
it. The disk operating system will, of course, 
be overlaid by BASIC. When you're through 
with BASIC, jump to the disk bootstrap to 
recopy the disk operating system back into 
memory. With BASIC versions 4.0 and 
above, type: 

DEFUSR=&HE900: X = USR(9) 
[carriage return]. 

For earlier versions type: 

POKE 65,0: POKE 66,233: X = 
USR(9) [carriage return]." 







tNEU MEXICO 


TECH. SOCORRO. NM 9890J. 505-835-5619 






BASIC 


EQU 


4020H 


S START OF UPPER BLOCK 






BASEND 


EClU 


7FFFH 


(END OF UPPER BLOCK 






BEGIN 


EQU 





; START OF LOUER BLOCK 


4000 


210000 


start: 


LXI 


H. BEGIN 


(DESTINATION ADDRESS 


4001 


112040 




LXI 


D.BASIC 


(START OF UPPER 


4006 


01FF7F 




LXI 


B.BASENE 


(END OF UPPER 


4009 


lA 


NEXT! 


LIlAX 


D 


(GET BYTE FROM UPPER BLOCK 


400A 


77 




MOW 


M.A 


(PUT IN LOUER BLOCK 


400B 


23 




INX 


H 


(INCREMENT POINTERS 


400C 


13 


INX 


n 






400D 


79 


MOW 


ArC 


;CHECK FOR END 


400E 


93 




SUB 


E 


(SUBTRACT LOUS 


40or 


78 




MOV 


A.B 




4010 


9A 




SBB 


D 


(SUBTRACT HIGHS 


4011 


D20940 




JNC 


NEXT 


(CONTINUE IF NOT DONE 


4014 


C30000 




JMP 


BEGIN 


(DONE. START PROGRAM 



Listing 1 : Program to move previously relocated MITS BASIC back where it 
belongs when using a North Star floppy disk. To move the original program, 
the parameters must be changed. BASIC must be set to hexadecimal 0000, 
BASEND to 3FFF, and BEGIN to 4020. 



modem / 'mo • dam / [modulator 
+ demodulator] n - s : a device for 
transmission of digital information 
via an analog channel such as a tele- 
phone circuit. 



those of us who live on the North American continent 
are blessed with an incredible non-natural resource 
consisting of a gigantic web of tiny copper wires linking 
virtually all of our homes and businesses together into 
the greatest telecommunications network in history. 
The Bell System and over 1600 independent 
telephone companies have been stringing wires 
and microwaves nearly everywhere for up to 
100 years. Now, the 80-103A Data 
Communications Adapter brings 
this amazing network to 
S-100 Micro 
Computers. 




The 

80-1 03A Data 

Communications 

Adapter is more than 

just a modem. It is a complete 

data communications sub-system 

combining on a single S-100 board 

functions which formerly required a 

modem, an automatic calling unit, and serial 

and parallel interfaces. This fully programmable 

unit gives you flexibility never before available at such 

a low cost. Fully assembled, tested, and burngd in with 

full documentation and our standard 90 day warranty, the 

iO-103A is available at retail computer stores across the country 

for only 279.95 



D.C. Hayes Associates Inc. 

P.O. BOX 9884 • ATLANTA, GA. 30319 • (404) 231-0574 

Dislfibutea in Canada by TRINTRONICS LIMITED, Toronto 



Circle 155 on inquiry card. 



July 1978 & BYTE PuUkaliom Inc 119 



Continued from page 1 1 

RSX-11 and DOS-1 1 variants of the 
same editor and can testify to tine useful- 
ness of the scope support features built 
Into the newer versions. One goes 
through a rather large annount of hassle 
with DEC to get the software for RTII 
(pricing is never very clear), but the 
result is fairly worthwhile. If you guys 
ever get a version of TECO running, I 
have an ELIZA demo that runs in it, just 
to show you a bit of what can be done 
with an editing language. 

Glenn C Everhart 

21 1 Great Rd 

Maple Shade NJ 08052 



IS THERE ANY CP1600 INTEREST? 

Have any of your multitude of read- 
ers expressed an interest in the General 
Instrument CP1600 chip and their 
GIMINI microcomputer? I have been 
Interested in this processor ever since 
Its development and would like to 
communicate with others on the subject. 
I was recently talking to one of the 
people at General Instrument's Hicksville 
plant and he was telling me about their 
latest offering, which is a single card 
32 K byte (addressed as 16 K words) 



implementation of this processor in- 
cluding read only memory operating sys- 
tem. This card is to be, in most cases, 
available as a fully assembled, burned in 
and tested card for original equipment 
manufacturer type applications. He also 
said that it might be possible to discuss a 
hobbyist type kit, unassembled, perhaps 
with fewer chips and capabilities and 
also less expensive. I would like to hear 
from anyone else who is interested in 
this powerful 16 bit processor (which 
uses a very PDP-11 like instruction set) 
and possibly talk again to General Instru- 
ment about interest in the hobbyist kit 
version. 

Brian D McCullough 

Site 9, Box 37 

RR2 

Sherwood Park, Alberta 

CANADA T8A3K2 



MULTIPROCESSORS 

ARE BECOMING 
EASIER TO DESIGN 

The article, "The Intelligent Memory 
Block" by K Castleman in the March 
1978 BYTE, page 186, was an interest- 
ing and an enlightening system design 
concept. However, his premise that the 
current development of multiprocessing 




$7 95 

T.Y. CROWELL 

10 East 53rd St. , New York, NY 10022 



CCMPUTIER 
CAPIERS 

From the acclaimed New Yorker series 
— now expanded for book publication. 

Thomas Whiteside 

"Anyone contemplating a life in strictly modem crime 

or who is worried about those who are should read 

Thomas Whiteside's guide."— john kenneth galbraith 

An alternate selection of Book-of-the-Monfh, 

Fortune, and Macmillan Book Clubs. 

2nd printing before publication. 



systems is lagging is no longer relevant. 
This is because of the mechanisms on 
many new microprocessors. 

National's 8060 and Motorola's 6801 
and 6809, for example, have the neces- 
sary on-the-chip hardware for bus access 
control. This allows for two or more 
microprocessors to be interconnected 
to perform different tasks on a time and 
memory share basis. Intel's new 16 bit 
microprocessor, 8086, is interesting 
because of its software control feature 
in multiprocessor applications. A special 
1 byte prefix attached to any instruction 
can compel the processor to assert a bus 
lock signal for the duration of the 
instruction operation, thereby allowing 
processors to share resources. By using 
these new microprocessors the memory 
block can now be intelligent but with 
a lot less hardware and timing strin- 
gency. 

John C Peterson 

Jet Propulsion Lab 

Pasadena CA 91103 



FOR SOME, 
HIGH PRICE=NO SALE 

Thank you very much for your 
editorial "Don't Ignore the High End 
. . . .or My Search for Manuscript 
Editing Paradise" which appeared in the 
March 1978 BYTE, page 6. 

I feel compelled to write to you 
because my thinking has been parallel 
to yours on this same topic and for the 
very same reasons. 

I started out with the idea that elec- 
tric typewriters have been around for 
many years; there is a market for them 
and the manufacturers have been able 
to make profits. 

These days we have a lot of very 
good and very cheap electronics so that 
it seems reasonable to expect electric 
typewriters with inbuilt memories and 
editing capabilities at reasonable prices. 
The price would also be increased by 
video displays and magnetic tape storage 
devices, but I do not expect that it 
would be anywhere near the $8000 
which you mention. The potential 
market for reasonably priced goodies 
may well include all those people around 
the various university campuses who 
type and retype dissertations, thou- 
sands of articles for publication in 
journals (including BYTE) and term 
papers. If I could get one with insert 
and delete capabilities for around $700 
I would go out tomorrow morning and 
get one right away. But that day seems 
to be rather remote at present. 

Philip S Barker 

59 Acadia Bay 

Winnipeg Manitoba 

CANADA R3T3J1 

There is a bit of a difference between 
an output peripheral (the typewriter) 
and a complete computer system with 
soft copy displays, magnetic auxiliary 
storage and lots of memory. 



120 July 1978CIBYTE Pubiications Inc 



Circle 81 on inquiry card. 



620/L VARIAN COMPUTER 
INFORMATION AND PARTS NEEDED 

We have a VARIAN 620/L which has 
been loaned to our computer center by 
one of our teachers. We are writing to 
find out if there are any readers of your 
publication who can help us locate 
additional plug in boards, either stuffed 
or unstuffed, for this machine so that 
we can mal<e more effective use of it. 
We would appreciate hearing from any- 
one who may be willing and able to help 
with any aspect of this machine. 

Norman Lee, Asst Prof 

Electronics-EDP 

College of The Albemarle 

Elizabeth City NC 27909 



DRAMA REQUIRES SPEECH 
AS WELL AS ACTION 

I was delighted to see the article by 
Gerrard, Ghent, Hemsath and Seawright 
(June 1978 BYTE, page 153) describing 
a simple modification to the Processor 
Technology VDM board which results 
In a greatly enhanced graphics capability 
for the small computer user. 

It may be of interest to a number of 
readers that this same modification is 
also quite useful for displaying and 
editing the control parameters for the 
Computalker Model CT-1 Speech Syn- 
thesizer. With a vertical resolution of 
208 lines, it is possible to display up to 
three CT-1 parameters simultaneously 
with 6 bits resolution on each. The 
horizontal resolution of 64 is sufficient 
to see more than Vi second of speech 
data at a time, plenty of display for good 
editing. 

We are currently exploring the 
possibilities of using such a graphics 
display in connection with a digitizer 
pad, which will make it much easier 
to produce good quality speech output 
with the Computalker board. 

Lloyd Rice, partner 

Computalker Consultants 

POB 1951 

Santa Monica CA 90406 

(213)392-5320 



WORD OF A BETTER SORT 

As a computer science major inter- 
ested (when I find the time) in getting 
into personal computing, I enjoy reading 
BYTE. In general, the material is worth- 
while and educational, but in your April 
1978 issue I was greatly disappointed to 
find one of the worst methods for 
sorting an array of items that I have ever 
seen published. Rene Pittet's algorithm, 
presented in "Programming Quickies," 
page 148, is a slow variant of the ubiqui- 
tous bubble sort. I am writing this letter 
to infornn your readers that there are 
much better sorting methods around, 
including some no more difficult to code 
or to understand. 

A well known method (which is 



about four times as fast as the one Pittet 
presented) is called straight insertion 
sort. To understand how it works, ob- 
serve that at the beginning of each 
iteration of the FOR-NEXT loop, the 
first 1-1 elements of the array are already 
in sorted order. The body of the loop 
merely inserts the Ith element into its 
correct position in that initial sorted 
segment. My code segment, which 
follows, replaces the actual sorting part 
of Pittet's code. 

Insertion sort is probably the method 
of choice when less than 30 items are 
being sorted — it is easy to write and to 
debug and incurs very little overhead. 
However, it can be shown that the 
amount of time required to sort N items 
using this algorithm is proportional to 
N*N. Thus, if sorting ten items take 100 
units of time, 1 000 items will take about 
10000 units of time! Many algorithms 
exist which require an amount of time 
proportional to N times the logarithm of 
N. I refer the interested reader to a 
book, which all hobbyists should read 
anyway, by Kernighan and Plauger: 
Software Tools. They describe the quick- 
sort algorithm, the generally recognized 
method of choice in a wide variety of 
applications. Mathematically inclined 
readers who want to know "everything 
you ever wanted to know" about sorting 
(and searching) should refer to The Art 



171 KEH STIllGHT lISnTIOl SUIT: PJTS THE ZLEIIEIIS 

172 BE!1 1(1) THVOOCR i (!) I ITO iSCEHDIir. OlDEi. 
17J lER 1: LOOP COUITIi - ELENEVT OP I TO BE 
17« lEII IISEBTEO iEIT 

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laO POB I ' 2 TO If 

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2J0 J - J - I 

235 PER UBTIL J = 

21*0 IP J > THEB 20S 

250 Jt [J*1) * R 

260 BRIT 1 



of Computer Programming, Volume 3: 
Sorting and Searching, by Donald E 
Knuth. 



Neal D McBurnett 

POB 4173 

Brown University 

Providence Rl 02912 



WHY NOT JUST USE THE PHONE? 

I was pleased with Mike Wilber's 
article on CIE standards ("CIE NET: 
Part 1, The Beginnings" February 
1978 BYTE, page 14) and look forward 
to seeing more in the same vein. How- 
ever, I was not equally taken with Jeff 
Steinwedel's article ("Personal Com- 
puters in a Communications Network" 
February 1978 BYTE, page 80) on the 



ELF 11 by 
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Learning Breakthroughi 

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July 1978 e BYTE Publications Inc 121 



How to say 

low-cost data tablet/digitizer 

in two words. 



Bit Pad 
Bit Pad 
Bit Pad 
Bit Pad 
Bit Pad 



TM 



TM 



TM 



TM 






BTTP«B 



5T'. .,•: ■''- 




Bit Pad is the low-cost digitizer for small computer 
systems. Better than a joystick or keyboard for entering 
graphic information, it converts any point on a page, any 
distance into its digital equivalents. It's also a menu for 
data entry. You assign a value or an instruction to any 
location on the pad. At the touch of a stylus, it's entered 
into your system. 

Who can use it? Anyone from the educator and the 
engineer to the hobbyist and the computer games 
enthusiast. The data structure is byte oriented for easy 
compatibility with small computers, so you can add a 
power supply, stand alone display, cross-hair cursor 
and many other options. 

Bit Pad by Summagraphics. The leading manufac- 
turer of data tablet digitizers. Bit Pad. The only words 
you need to say when considering digitizers. 

■ >Sunmiadu]fihic6 

-E-'iF- ^ ' corporation 

::!!:?:: 35 Brentwood Ave,, Box 781, Fairfield, CT 06430 
^' """" ^ Phone(203) 384-1344, TELEX 96-4348 



use of RF in a data exchange network. 
His generalities do no justice to tine 
enormous technical, political and finan- 
cial complexity of such a system. It is 
unfortunate that someone who must 
know quite a bit on this subject would 
author oversimplifications which could 
lead less well informed persons to believe 
that such a system is really a practical 
option. 

Anyone who plans to propose that 
the FCC allocate 1 MHz of precious 
VHF or UHF spectrum for a short haul, 
fixed, unattended, personal radio 
communication service should be pre- 
pared to be laughed out of Washington. 
First, just where does Mr Steinwedel 
suggest that this 1 MHz come from: 
amateurs, government, broadcasters? 
Don't count on it! The fact is that 
there is nothing like a 1 MHz block 
available below 900 MHz. Second, all 
services are allocated frequencies on the 
basis of international standards and 
demonstrated need. How can anyone 
demonstrate the need for a frequency 
hungry radio network to link homes 
around town so we can all play Star Trek 
together? How would he reply when 
asked, "Why not just use the phone?" 
Third, Mr Steinwedel totally ignores 
the high cost of such a system. This is 
probably due to the fact that amateurs 
don't have to pay first class technicians 
to maintain their equipment. Why do 
you think the cost of mobile telephone 
is so high? Finally, the suggestion that 
the FCC would authorize this service 
to employ totally unsupervised trans- 
mitters exhibits unfamiliarity with one 
of the prime principles of FCC regu- 
lation. That is, who is going to pull the 
plug when the thing gets stuck in trans- 
mit mode? Every chapter of the FCC 
Rules and Regulations expounds on this 
principle at length under the heading of 
"Operator Requirements." The cases 
where the FCC has authorized totally 
unsupervised transmitters are so few as 
to not be worth noting. In short, why 
don't you just use the phone? 

I don't want to give the impression 
that I am totally against digital radio 
communications. It is fine by me if 
amateurs wish to combine hobbies. I 
personally would love to help set up an 
intercity tropo or satellite link for CIE 
use. However, I would not be so bold as 
to suggest that it would be cheaper than 
"Ma Bell." 

Anyone who wishes to explore the 
possibilities of digital exchange and 
calling by radio should obtain a copy of 
the International Telecommunications 
Union CCIR Study Group 8 Draft 
Recommendation #493 which proposes 
some international standards for similar 
systems. I would also suggest that any- 
one interested in writing CIE standards 
should first take a long look at standards 
accepted by the ITU and other organi- 
zations so that international compati- 
bility can be maintained. 

Donald R Newcomb 

819 Bayou Blvd 

Pensacola PL 32503" 



1 22 July 1978 © BYTE Publications Inc 



Circle 352 on inquiry card. 



College 
Sports Report 



Grinnell Wins Second Midwest 
Regional Programming Competition 

Grinnell College of Grinnell lA barely 
nosed out DePauw University of Green- 
castle IN in the Second Midwest Re- 
gional Programming Competition held at 
Taylor University, Upland IN, April 1 
1978. The host team, Taylor, finished 
third and Wabash College of Crawfords- 
ville IN was fourth. Grinnell's 2 person 
team led by Scott Parker of Champaign 
IL and sponsored by Prof Mark Grundler 
defeated DePauw's squad by only three 
points in the 4 person, 4 hour competi- 
tion using Taylor University's DEC time- 
sharing system. However Evansville Uni- 
versity used their IBM 360 over tele- 
phone lines for the competition. 

Each team had only one 300 charac- 
ter per second printing terminal on 
which to write, test and debug their pro- 
grams. A team of six judges led by chief 
judge Bruce Gaff of Plycom Industries 
(Plymouth IN) and Jere Truex (Upland 
IN) reviewed the solutions written in 
BASIC and indicated if the solutions 
were correct or incorrect. The scoring 
method included the number of prob- 
lems, the time required to complete the 
solution, and the number of judged runs 
submitted. 

The four problems posed included 
writing check amounts in words, screen- 
ing inaccurate data from an electronic 
instrument for accuracy, connecting 
pairs of points in a geometric plane, and 
retrieving prices from descriptions in a 
catalog. 

Although 14 teams from seven mid- 
western states were expected, schedule 
changes and other factors caused some 
teams to miss the competition. In addi- 
tion to the four teams already men- 
tioned, others competing were the Uni- 
versity of Wisconsin/Platteville, Asbury 
College of Kentucky, plus Grace College 
and Rose-Hulman Institute from Indiana. 

Next year the Midwest Region will 
be held at Rose-Hulman or Taylor Uni- 
versity. It is hoped that a National 
BASIC competition between regional 
champions will be held at a later date. 
Taylor University had two freshmen on 
their third place team and other schools 
had freshmen participating also, so it Is 
anticipated that next year's competition 
will be even more strongly contested. 

Taylor's young team included senior 
Steve Olsen from Wyckoff NJ, junior 
Mark Tomlin of West Milton OH, plus 
freshmen David Woodall of Marengo IL 
and Stan Rishel of Kalamazoo Ml. The 
alternate members were freshmen Cory 
Waller of Franklin Lakes NJ and Mark 
Collins of Indianapolis, who missed the 
competition because of illness." 



DATALYZER ... a 24 channel 
Logic Analyzer for your SlOO Bus 




24 Channel LOGIC ANALYZER, complete with 2 cards and 3 sets of probes. 

Features 

— 24 channels with 256 samples each. 

— Display of disassembled program flow. 

— Dual mode operation - external mode analyses any external logic 
system. Internal mode monitors users data and address bus. 

— Selectable trigger point anywhere in the 256 samples. 

— 0-16 bit trigger word format or external qualifier. 

— SIVlHz sample rate 

— Synchronous clock sample with coincident or delayed clock mode. 

— User defined reference memory. 

— Displays and system control through keyboard entry. 

— TTL Logic level compatible (15 pf and 15 )ja typical input loading.) 






Displays in Binary 



Displays in Hex 



Display of disassembled 
program flow. 



The DATALYZER 

Designed to plug easily into your S-100 Bus, the DATALYZER is a 
connplete system — for only $595. Display of disassembled program 
flow is a standard feature, not an extra. And the low price includes 30 
logic probes, so you can hook up immediately, without additional 
expense. 

The DATALYZER is available in kit form ($595), and as a fully 
assembled device on two PCB's ($695). Operators' manual $7.50. A 
substantial warranty, and the Databyte, Inc. commitment to service 
make the DATALYZER a worthwhile investment. 



Databyte, Inc. 



7433 Hubbard Avenue 
Middleton, Wisconsin 53562 
Tel: (608) 831-7666 



Circle 86 on inquiry card. 



)uly 1978 ©BYTE Publications Inc 123 



How to Choose a Microprocessor 



Lou Frenzel 
Heath Company 
Benton Harbor Ml 49022 



All personal and hobby computers are 
microprocessor based. That is, they use a 
single processor integrated circuit chip. 
One of the most important decisions you 
will ever make in purchasing a personal 
computer is choosing the type of micro- 
processor. The semiconductor manufacturers 
have provided computer designers with a 
wide range of microprocessing units having 
varying degrees of power and sophistication. 
As a result, there are at least a half dozen 
different processors available in hobby 
computers. This wide variety of products 
mal<es your choice somewhat flexible, or 
at least it seems that way. In reality, having 
so many processor styles to choose from, 
your decision becomes much tougher. If 
you are a beginner, it may be particularly 
difficult to make an intelligent choice. The 
purpose of this article is to provide you with 
some guidelines in making this important 
decision. The emphasis is on how to choose 
the best microprocessor for you when pur- 
chasing a personal computer. 

What's Available 

Below is a list of all of the available 
microprocessor architectures and their pri- 
mary manufacturers. 

Intel 8080, 8085, 8048, 8086 

Motorola 6800 

MOS Technology 6502 

Zilog Z-80, Z8000 

Signetics 2650 

RCA 1802 

Fairchild F8, 9440 

MOSTEK 3870 

Intersil 6100 

Texas Instruments 9900 

National Semiconductor SC/MP, PACE, 8900 

DECLSI-n 

Data General microNova 

General Instrument 1600 



With this wide variety, is it any wonder 
that it is a difficult choice? Yet with all of 
these available devices, the choice narrows 
down rather quickly when several important 
factors are considered. What makes things 
even more confusing is the fact that many of 
the above microprocessors will undergo 
changes and improvements. Semiconductor 
manufacturers will also develop and intro- 
duce even newer improved microprocessors. 
The whole microprocessor business is a 
dynamic one. Changes occur almost daily. 
The biggest dilemma is not so much the 
changes themselves but the rapidity with 
which they occur. Today you may make a 
decision to use a particular microprocessor 
only to find that six months later the choice 
is apparently incorrect because a newer, 
better, improved device has become avail- 
able. There is no complete solution to this 
problem. The rapid changes in this field 
will continue to occur. For that reason, 
you must make a choice and stick with it. 
You must attempt to select a device that 
has the greatest longevity potential as well 
as one that meets the criterion for perform- 
ance in your application. You must not let 
the rapidly changing technology paralyze 
your decision making process. It is best to 
choose among the presently available devices 
and take your chances with the future. To 
obtain the most value from your personal 
computing system, you must select a micro- 
processor that meets your immediate needs 
but offers future potential as well. 

Selection Criteria 

There are many factors that go into the 
process of selecting a microprocessor. You 
should consider all of these factors even 
though some of them affect you only in- 
directly. You should also be influenced by 
the factors that ordinarily would interest 



124 July 19780BYTE Publications Inc 



only the designer. Below are listed some 
of the key elements in choosing a 
microprocessor. 

Cost 

Cost is always a major consideration in 
choosing a microprocessor. However, of all 
the factors involved, this is one that the user 
should be least concerned about. Cost is 
primarily the concern of the computer 
manufacturer. Most microprocessor inte- 
grated circuits are in the same price range; 
and the cost of the microprocessor itself is 
only a fraction of the overall cost of the 
computer system. The cost of memory and 
peripherals is far more than the cost of the 
processor. Thus for purposes of our dis- 
cussion here, cost is irrelevant. 

Speed 

One of the factors considered in the 
evaluation or comparison of computers is 
processing speed. This is the rate at which 
instructions are executed. While speed is 
primarily a function of the clock frequency 
and the upper frequency limit of the micro- 
processor itself, it is also affected by the 
memory speed and the architecture of the 
processor. Most modern microprocessors are 
not known for their processing speed. After 
all, most microprocessors are metal oxide 
semiconductor (MOS) circuits which are 
inherently slower than bipolar (TTL) cir- 
cuits. Over the years great improvements 
have been made in the speed of MOS cir- 
cuits. The slow "P channel" circuits have 
been gradually replaced by smaller and 
faster "N channel" circuits. Continuing 
developments in the N channel process 
promise even further improvements in 
speed. Speeds approaching bipolar levels are 
achievable. If processing speed is the most 
important criterion, then bipolar circuits 
should be selected over MOS microproc- 
essors. Speed is of little or no consideration 
in choosing a microprocessor-based personal 
computer. Most MOS microprocessors used 
in personal computers execute an instruction 
within several microseconds which is fast 
enough for most applications. 

While processing speeds can vary as much 
as four to one among MOS microprocessors, 
the difference is almost unnoticeable. For 




From the machine and assembly 
language programmer's point of view, 
the Signetics 2650 processor shown here 
is often considered to be a superior 
machine. But it has never become popular 
in the personal computing field, most 
likely because it entered the 8 bit market- 
place later than the major contenders. 
This photograph was supplied by Sig- 
netics. 




The Digital Group leaves out no major microprocessor choice. While 
their emphasis is on the Z-80 processor, they cover all bases with options 
for 8080, 6800, 6502 and Z-80 processor boards. This photo, supplied by 
Digital Group, shows a board which features the 8080 processor. 



July 1978 ©BYTE Publications Inc 125 



Circle 43 on inquiry card. 




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r 




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The KIM to S-100 bus 
Interface/Motherboard 

• Combines the power of the 6502 with the flexibility of 

the S-100 bus 

• Attaches to any unmodified KIM 

• Complete interface logic and fully buffered motherboard 

in one unit 

• Onboard regulation of power for KIM 

• Eight slots of S-100 compatibility for additional RAM, 

Video and I/O boards, PROM Programmers, Speech 
processors . . . 

• Includes all parts, sockets for ICs, one 100 pin connector, 

and full Assembly/Operating documentation 

♦ Kit $125, Assembled $165 

♦ All units shipped from stock 

FORETHOUGHT PRODUCTS 

P.O. Box 386-F pi^ 

Coburg, OR 97401 UgJ^j 



example, most hobbyists use the BASIC 
language. The speed of the microprocessor 
will definitely determine the length of time 
that it takes to execute a program. However, 
with an interpretive language such as BASIC, 
an order of magnitude difference in execu- 
tion speeds is frequently almost unnotice- 
able to the user. While it may take 200 iis 
to execute a program on one computer and 
20 /is on another, the user is often totally 
incapable of recognizing the difference. 

The real value of speed comes when your 
application requires it. If your applications 
involve lengthy, complex mathematical 
operations or highly complex real time 
functions, speed may be an important con- 
sideration. Otherwise, speed is one factor 
which you could practically ignore in the 
selection of a personal computer. Few per- 
sonal computer manufacturers know how to 
specify it, let alone mention it. 

Computing Power 

Computing power is a rather nebulous 
designation that refers to the power of the 
instruction set and architecture of the com- 
puter. Computing power also effectively 
involves speed as discussed above. Yet 
computing power is far more important 
than raw speed in determining the capa- 
bilities of a microprocessor. 

It is difficult to provide any specific 
guidelines for determining whether one 
microprocessor is more powerful than 
another. However, as a general guideline 
there are several factors to look for in 
determining which microprocessor has the 
greatest power. These factors are: number of 
instructions in the instruction set, number of 
working registers, and number and type of 
addressing modes. Those microprocessors 
with the greatest numbers of instructions, 
registers, and addressing modes are essentially 
the more powerful microprocessors. They 
can accomplish more complex operations 
in less time than other microcomputers with 
lesser characteristics. 

It is the wide variation in architectures 
which makes the choice of a microprocessor 
interesting. In some cases, a superior in- 
struction set, more flexible register organiza- 
tion and more addressing modes can offset 
the superior computing speed of another 
microprocessor with a simpler architecture. 
There are never any clear cut answers to 
the question of which microprocessor is 
the most powerful since usually the answer 
lies in a specific application. When a partic- 
ular application can be defined, the choice 
of microprocessor can be optimized. How- 
ever, when choosing a microprocessor-based 
general purpose computer which must be 



1 26 July 197S e BYTE PuUicatisns Inc 



Circle 140 on inquiry card. 



Circle 265 on inquiry card. 



useable in a wide range of applications, the 
speed and computing power consideration 
becomes fuzzy at best. 

Second Sources 

Another way to assess the value of a 
microprocessor is to consider the second 
sources. Second source refers to a manu- 
facturer other than the original manu- 
facturer, producing the same device. When a 
semiconductor manufacturer introduces a 
new microprocessor, he attempts to capture 
as much of the marl<et as possible with 
various features and pricing strategies. 
However, one of the strategies that works 
best is if competing manufacturers choose 
to make the same device. These secondary 
manufacturers will compete with the pri- 
mary manufacturer. Despite this competi- 
tion, it is usually the original manufacturer 
who benefits from this situation. It provides 
alternate sources. The competition creates 
pricing advantages. In addition, the relia- 
bility of supply is improved. One way to 
determine the popularity and widespread 
use of a microprocessor is to determine its 
second sources. The more second sources 
that a device has, the more widely it is used 
and the more competitive is the pricing. 
Don't overlook this as a way of choosing a 
microprocessor. 

Popularity 

It may seem almost ludicrous to include 
such a general and seemingly meaningless 
criterion for selecting a microprocessor as 
popularity. Yet this rather inexact factor is 
important. Most people tend to want to go 
along with the crowd. They want to select 
devices that are well known and widely 
used by others. For that reason, you cannot 
overlook the popularity factor. Most people 
feel that a device that is popular and widely 
used must have something going for it. This 
tends to make their own choice easier. In 
effect, they are relying upon the decisions 
of many others to back up their own 
decision. This is why Chevrolet sells more 
cars than any other US manufacturer. 
Popularity in computing also has benefits 
with regard to availability of software. 

The choice of a microprocessor is also 
largely emotional. Even though a device may 
not have the benefits of software avail- 
ability, speed and computing power, the 
device may be highly regarded. This may be 
because of the reputation of a particular 
manufacturer or a particular unique feature. 
Many times the features or benefits are per- 
ceived rather than real. A strong sales pitch 
by a trusted friend or respected source can 
also easily sway an individual's choice. In 




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selecting a microprocessor, you are often 
buying mystique or potential rather than 
real practical computing capability. The 
thought of having the newest, best, fastest, 
most powerful microprocessor is a strong 
selection inducement. While these factors 
will no doubt influence you, you should 
attempt to be more practical, realistic and 
analytical in the selection of a microproc- 
essor for your own personal computer. 

Documentation 

Documentation refers to all of the 
written material available for a particular 
microprocessor. This includes magazine 
articles, books, courses, manufacturers' 
literature and any other printed sources. 
Good documentation is hard to come by 
and often it will make the difference be- 
tween failure and success in getting your 
system to work. You will get more value 
from your own investment if you have 
plenty of written sources to refer to and to 
help you in applying it. This is particularly 
true if you are a beginner. The more sources 
of information you have for the micro- 
processor, the easier it will be for you to 
learn to use it. You should always con- 
sider this factor before making your final 
decision. 

Upwards Compatibility 

Upwards compatibility refers to the 
future of a given microprocessor. It tends to 
indicate that a particular microprocessor will 
eventually be upgraded or replaced by a 
compatible device. Computer manufacturers 
found out early that upwards compatibility 
was an extremely important part of their 
development and marketing strategy. The 
upwards compatibility factor is tied to soft- 
ware. Individuals who purchase computers 
proceed to develop considerable amounts 
of their own application software. If at 
a later date they decide to replace that 
computer, they must take into consideration 
the status of their applications software. If 
the replacement computer is upwards com- 
patible with the previous computer, their 
present software will run on the new com- 
puter. Because of the significant amount of 
time and money invested in software, the 
desirability of upwards compatibility is 
extremely important. If an entirely different 
microprocessor or computer is selected, it 
may be necessary for the users to completely 
convert or abandon their present software. 
This is highly undesirable since it involves 
throwing away a considerable investment. 

When considering a microprocessor, you 
should examine the concept of upwards 
compatibility. Will the microprocessor you 



128 



July t978«jBYTE Publiciliom Inc 



Circle 319 on Inquiry card. 



Circle 183 on inquiry card. 



select eventually be replaced and upgraded 
by a compatible improvement? If so, it is 
probably a good choice. This means that 
you will obtain valuable usage from your 
present computer but then ultimately up- 
grade to a more powerful system at a later 
date without any loss of software capability. 
Most of the major microcomputer manu- 
facturers are quickly learning the importance 
of the upwards compatibility concept. 

Software 

It seems almost unnecessary to mention 
the importance of the software factor in 
choosing a microcomputer. Even a beginner 
quickly learns that the microcomputer 
hardware itself is useless without good soft- 
ware. This means not only good systems 
software that allows you to develop your 
own applications programs, but also the 
availability of a wide range of "canned" or 
predeveloped programs which can be run on 
the computer. Most computer hobbyists 
want to write and develop their own pro- 
grams. But the value of their systems is 
higher if they can also readily obtain other 
software that will run on their computers. 
All things considered, software and Its 
availability is by far the most important 
decision making factor in choosing a 
microprocessor. 

There are two software considerations 
which you should make. First, how easy is 
the microprocessor to understand and 
program? Second, how much software is 
available for that particular device? In the 
first case, the simplicity of the instruction 
set and architecture makes a great difference 
in learning to use a microcomputer. If the 
instruction set is straightforward and the 
architecture textbook-like, the microcom- 
puter will be easy to program and use. Even 
a beginner will learn to use it quickly and 
obtain satisfactory results. 

In the second case, how much software is 
available for the microprocessor? If the 
microprocessor is popular and very widely 
used, chances are there is a tremendous 
amount of software available. Programs are 
listed in magazine articles or are available 
for sale. Regardless of the source, if software 
is available for the microprocessor, then the 
choice is a good one. The lack of available 
software is a clear indication that the proc- 
essor is not widely used and that you will 
have to develop most of the software your- 
self should you choose it. Software should 
be your single most important consideration 
in choosing the microprocessor. All other 
factors, speed, cost and computing power 
are practically irrelevant or at least far less 
important than the software consideration. 



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Circle 145 on inquiry card. 



)uly 197g®BYTE Publicilions Inc 



129 



(o) 




(b) 




(c) 




Shown at (a) is the Heathkit H8 computer, which uses the 8080 processor 
to provide generai purpose computing capability. It Is typical of a number of 
units based on the popular 8080, Z-80, 6502 or 6800 processor integrated 
circuits. Other examples of personal computers Include the Cromemco Z-2 
(b), and the Equinox 100 (c). 



The Big Four 

Of all the microprocessors listed earlier, 
four are clearly the most popular and widely 
used. It is probably safe to say that these 
four devices account for more than 90 per- 
cent of all microprocessors used in personal 
computing systems. It is strongly recom- 
mended that you choose one of these four 
devices when selecting your microcomputer. 

The microprocessors most widely used in 
hobby and personal computers are the 8080, 
the 6800, the 6502 and the Z-80 in that 
order. You won't go wrong if you choose 
one of these four microprocessors. A con- 
siderable amount of software is available for 
each and there is evidence to support the 
concept of upwards compatibility. Let's 
take a look at each of these devices and 
analyze its present capabilities and future 
potential. 

8080 

The Intel 8080 microprocessor was the 
first of the second generation 8 bit micro- 
processors. Because it was first, it readily 
captured a large portion of the 8 bit proc- 
essor market. Later second generation 
microprocessors such as the 6800 had a 
more difficult time in penetrating the mar- 
ketplace simply because of the great lead 
that Intel held. The 8080 was announced in 
1973 and even today despite inroads by 
other 8 bit microprocessors, the 8080 is 
still "king of the hill." 

While the architecture, speed and com- 
puting power of the 8080 are not spectacular 
when compared with other chips, it is 
nevertheless a useable device. It has proven 
its worth and value time and time again 
not only in dedicated industrial cohtrol 
applications but also in stand alone general 
purpose microcomputers. It is so widely 
used and well documented that it is by far 
one of the best choices you can make. In 
addition, there is more software available for 
the 8080 than for any other 8 bit micro- 
processor. While exact data is difficult to 
obtain, an estimate I have seen claims that 
over 60 percent of all 8 bit microprocessors 
in use are 8080s. 

Another factor that the 8080 has going 
for it is that upwards compatible devices 
are available. Intel's new 8085 microproc- 
essor is an improved 8080. By using the 
8085, you can develop a microcomputer 
with greater capabilities than the 8080. The 
8085 uses fewer support chips since the 
clock and system controller functions nor- 
mally required for the 8080 are effectively 
built into the 8085. In addition, the 8085 
uses a single power supply eliminating the 
additional two supplies required by the 



130 



luly 1978 ©BYTE Publicitions Inc 



Circle 82 on inquiry card. 



8080. An added bonus is that the 8085 
operates at a higher speed and has several 
more instructions. 

Another upwards compatible device for 
the 8080 is the well known Z-80. This 
device is a newer and more powerful micro- 
computer with far greater capabilities than 
the 8080. Nevertheless, the Z-80 was de- 
signed to include the 8080 instructions so 
that software written for the 8080 will also 
run on the Z-80. The 8080 instruction set 
is in effect a subset of the Z-80 instruction 
set. The Z-80 is not only faster but has 
nearly twice as many instructions making it 
a far more powerful microprocessor. Like 
the 8085, the Z-80 requires fewer external 
support chips and only a single 5 V power 
supply in contrast to the 8080. 

Evidence of the popularity of the 8080 
can be demonstrated simply by listing the 
number of personal computer manufacturers 
who use the 8080. A probably incomplete 
list of manufacturers of 8080 systems 
includes: 

Digital Group 

E&L Instruments 

Equinox 

Heath Co (H8) 

IMSAI (8080) 

MITS (Altair 8800b) 

PolyMorphic 

Processor Technology 

Vector Graphic 
There are more 8080 based personal com- 
puters than any other type. 

Another consideration is the number of 
second sources available for the chip itself. 
As indicated earlier, the number of second 
sources is a clear evidence of the popularity 
of a particular microprocessor. Semicon- 
ductor manufacturers typically will not 
gear up to second source a device unless 
there is a large demand and an identifiable 
market for that device. A list of suppliers of 
the 8080 is given below. 

Intel (the original 8080 design) 

Advanced Micro Devices 

Texas Instruments 

National Semiconductor 

NEC (Nippon Electric) 

Siemens 

Again, there are more second sources 
for the 8080 than for any other 8 bit 
microprocessor. 

Another factor to consider is the bus 
design associated with the 8080 based micro- 
computers. The popular MITS Altair or 
S-100 bus is used by most of the manu- 
facturers incorporating an 8080. The S-100 
bus is in effect an 8080 bus. The signals 
defined on that bus are peculiar to the 
8080. The S-100 bus over the past several 



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Circle 137 on inquiry card. 



luly 1978 8 BYTE Publications Inc 131 



years has become nearly a standard. While 
not an official standard, it does neverthe- 
less provide the user with a wide choice of 
options and accessories for his 8080 based 
microcomputer. However, keep in mind that 
the Altair bus became a de facto standard by 
virtue of being the first widely sold design. 
Many manufacturers jumped on the Altair 
bus bandwagon when they started because 
it had a built-in marketing advantage; this 
helped snowball interest in the Altair bus. 
While the Altair (S-100) bus is certainly not 
an optimum choice, it is strong inducement 
to many individuals simply because so many 
people are using it and so many accessory 
products are available. By choosing an 8080 
microprocessor you will no doubt at the 
same time be choosing an S-100 bus. That 
isn't all bad. Keep in mind, however, that 
several 8080 designs on the market do not 
use the S-100 bus. Notably these are the 
Heathkit and Digital Group designs. 

6800 

The second most popular and widely used 
microprocessor is the Motorola 6800. It was 
announced almost a year after the 8080. 
Despite its time lag behind the 8080, the 
6800 has come from behind to capture a 
rather large following. While it is still not as 
widely used as the 8080, it is a clear-cut 
second place with many followers and 
supporters. 

The architecture of the 6800 is extremely 
simple. It is a classic, almost textbook-like 
design. Its instruction set is easy to learn 
and understand. And at the same time, it 
incorporates a variety of addressing modes. 
While it is slightly slower than designs like 
the 8080 or Z-80, the 6800 makes up the 
lack of speed in its superior instruction set, 
architecture and addressing modes. 

A wide variety of software has been 
developed for the 6800. This software is 
widely available to most 6800 users. 

The popularity of the 6800 can be illus- 
trated by the number of hobby and personal 
computer manufacturers using the 6800. 
A probably incomplete list of these is 
given below. 

Southwest Technical Products 

(SwTPC 6800) 
Wavemate 

Electronic Products Associates 
MITS (Altair 680b) 
Digital Group 
Motorola 
MSI 
Heath Company 



A list of second sources for the 6800 
chip is given below. 

Motorola 

American Micro Systems Inc 

Fairchild 

Hitachi 

Unlike the 8080, the 6800 does not 
appear at present to offer upwards com- 
patibility. It is possible that a more powerful 
6800 will be offered in the future. However, 
improved versions of the 6800 have been 
announced by Motorola. They include 
features such as on-chip clock and memory 
and higher speed versions. These improved 
versions will help lengthen the life of the 
6800. 

All in all, the 6800 is a well established 
microprocessor. You will certainly not go 
wrong in choosing this device in your 
microcomputer. 

6502 

The MOS Technology 6502 is essentially 
in third place in the hobby and personal 
computing field. This device is very similar 
to the 6800. There are a number of dif- 
ferences in that the 6502 does feature an 
on-chip clock, only one accumulator, and 
different indexed addressing modes. It 
is widely used in hobby and personal 
computers. 

Due to the large number of KIM-1 com- 
puters in the field, the 6502 does have an 
enthusiastic following of users and an in- 
dependent users' publication. 

Some of the personal computers using 
the 6502 are listed below. 

Ohio Scientific Instruments 
Apple Computer 
MOS Technology (KlM-1) 
Commodore PET 
Microcomputer Associates JOLT 

At the present time there are three 
sources for the 6502. These are MOS Tech- 
nology, Synertek and Rockwell. 

While the 6502 is way down the list in 
terms of popularity when compared with the 
8080 and 6800, it is still a widely used 
device. Like the 6800, it is simple to learn 
and use. It is a practical choice for a per- 
sonal computer. 

Z-80 

The Z-80 is one of the most popular and 
certainly the most talked about 8 bit micro- 
processor of 1976 and 1977. While it was 
introduced a number of years after the 8080 



132 )uly 1978 ©BYTE Publications Inc 



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Circle No. 314 on reply card 



irMCDRPOHATED 

A SUBSIDIARY OF SCOPE INC , RESTON, VA 

PRINTERS FOR SALE 

■A Liivll I tD QUANTITY OF USED 

Ll.ECTROSENSITIVE NON IMPACT PRINTERS 

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■AS IS WARRANTED TO WORK OR 

WILL RECONDITION TO LIKE NEW 
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PRINTER TERMINALS 
■IHESE PRINTERS OPERATE WITH 

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A SPECIAL COLOR MODULATOR FOR APPLE II USERS!: 
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over a minimum of 4 channels. Interfaces direcTly wltti 
the Apple II as well as mosT other micros, Comes with 
video cable and RF output stub coupler. Two-Toned cowl 
type decorator cabinet. Sue: 5.5cm i a. 5 cm i 1 1.5cm. 
Power; +SV. CurrenT approx. I ma. Self-powered with 4 
pencell batteries. Operating life In excess of 1000 hours 
or near shelt-life o1 baneries. Excellent stability. Precise 
frequency adjustment. Ho assembl y required except for 
installation of batteries, not supplied. MODEL MVX-500. 

AVAILABLE FROM YOUR LOCAL COMPUTER DEALER 
or direct trom ATV RESEARCH. COST including shipping 
anywhere in USA and Canada — $35.00. 



PIXE-PLEXER " An IC type video-to-RF modulator 
includes FM sound sub-carrier, color subcarrier and 
teparate R-Y and 8-Y inputs. Designed around the 
LM-IB89 chip. A designer's dream with full data sheets. 
Model PXP-45D0. Kit form. S24. 50 postpaid. 



■ PIXE-VERTER " 
interface module. 



The original computer video-to-RF 
Kit form: $8.50 Model PXV-2A 



I PHONE or WRITE TODAY. DIAL 402-387-3711. 



-^A^. 



l^B Broadway ATV Ressanch Dakota City, Nebr. 

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Circle 17 on inquiry card. 



SURPLUS ELECTRONICS 



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• Cabinets • XFMRS • Heat 
Sinks • Printers • Components 
Many other items 

Write for free catalog 
WORLDWIDE ELECT. INC. 
10 FLAGSTONE DRIVE 
HUDSON. N.H. 03051 
Phone orders accepted using VISA 
or MC. Toll Free 1-800-258-1036 
In N.H. 603-885-3705 



Circle 193 on inquiry card. 



Circle 312 on inquiry card. 



Circle 395 on inquiry card. 



aiiiiiiiiiiiiiiiii iiiiiiiii iiiiiiiii iiiiiiiiiiiiiiiiiiiiiiiiiiii nil iiiiiiiiiiiiii iiiiiii Ill Ml mil iii iniiiii iiiiiiiiiiiiiiiiiiiiii^ 

I Infinite Programming Possibilities | 



I Microcomputer Handbook by Charles J SippI defines tine 
j present state of computer technology very well, con- 
1 centrating on both hardware and software. Lucid and 
i complete glossaries are combined with a variety of 
I illustrations. Topics covered include: microcom- 
\ puters-where they are, what they are doing, and 

■ what is next; kits; distributed intelligence; and 

• why the new systems are easier to use. The 
; book was written by a computer industry lec- 
j turer and consultant and is highly recom- 
; mended for the intelligent lay person as well as 
I for professionals and experimenters. The glos- 

■ saries alone are worth the price of the book— 

• don't miss this one! This hardcover reference is 
i only $19.95. 




Top-down Structured Programming Techniques. What is [ 
structured programming? Clement L McGowan and | 
John R Kelly answer this question in their lively, : 
well-written book. Top-down Structured Program- : 
ming Techniques. Discover the three basic types i 
of flowcharts and how to optimize them. One j 
section deals with the best ways to manage pro- j 
grams being written by a team of programmers, j 
An important feature of this book is its univer- j 
sality: practically any program in any language | 
can be improved by using the ideas described | 
in it. 288 pp. $1 5.95 hardcover. j 

I 

For convenience in ordering, please use the order! 

form on page 83, writing in the books you want. j 



j HTT V- The Microcomputer Bookstore 

= BJ^L I ^B 25 Route 101 West, Peterborough NH 03458 

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CALL YOUR BANK CARD ORDERS 
TOLL FREE 1-800-258-5477. 



Circle 35 on inquiry card. 



BYTE Julv 1978 133 



(a) 




(d) 




(b) 




. 1 

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rcj 



Several firms manufacture microprocessor trainers like t/iese. The unit 
at (a) is an E&L Instruments IVII\^D-I 8080 based trainer, shown with a 
tape recorder for mass storage and documentation. The unit at (b) is the 
Heath kit ET3400 trainer, based on the 6800 design. The unit at (c) is the 
MOS Technology KIM- 1 single board 6502 computer, probably the most 
widely sold board in personal computer experimental circles. The unit at 
(d) is a Motorola 6800 training kit available from the manufacturer. (These 
photos supplied by the respective manufacturers.) The training computers 
tend to have limited memory and limited peripheral capability, but excel- 
lent documentation designed to train technical people in the operation of 
a particular computer and in general principles of computer controlled 
systems. 



and 6800, it has managed to capture a 
significant portion of the microprocessor 
marl<et. It has also been widely accepted in 
hobby and personal computing. Because 
it is essentially an improved and more 
powerful 8080, the Z-80 can be considered 
a part of the 8080 movement. Nevertheless, 
it deserves some attention on its own. 

Some of the personal computers using 
the Z-80 are listed below. 

Technical Design Labs 
Cromemco 
Digital Group 
Radio Shack 

The Z-80 also has two primary suppliers. 
These are ZiJog and Mostek. 

Since the Z-80 will run most 8080 soft- 
ware, it is an excellent choice with respect to 
software. Besides the upwards compati- 
bility and software factors, the Z-80 is also 
far more powerful. It runs at a higher speed, 
has a larger instruction set and more sophis- 
ticated addressing modes. The Z-80 is per- 
haps the best 8 bit microprocessor currently 
on the market. 

Despite these advantages, the several Z-80 
based processor boards developed as replace- 
ments for S-100 based microcomputers have 
not been all that popular. It is difficult for 
the owner of an 8080 based Altair bus 
microcomputer to justify a three or four 
hundred dollar expense simply to replace 
an 8080 processor with a Z-80. While you 
still maintain software compatibility, the 
Z-80 provides the additional benefits of 
greater computing power and speed. How- 
ever, most hobbyists do not require the 
greater power and computing speed. The 
capabilities of the less powerful 8080 are 
more than adequate. 

Choosing a microprocessor for a micro- 
computer design is an agonizing process. Yet 
once all of the factors are considered, the 
choice narrows down rather quickly. For a 
general purpose microcomputer, most de- 
signers circa 1975 to 1977 quickly identified 
the four choices given above. Choosing 
among them then becomes somewhat sub- 
jective. I was personally involved in making 



134 July 1978 © BYTE Publications Inc 



Circle 6 on inquiry card. 



a decision for tiie microprocessor of the H8 
Heathkit computer. When that choice was 
made in early 1975, the Z-80 was not 
available. The 6502 was a fairly new device 
and no second source was available. This 
narrowed the choice rather quickly to the 
8080 and 6800. At that time the 6800 had 
not penetrated the 8 bit market as much as 
it has now. As a result, not as much software 
and documentation support were available. 
Because of this, the 8080 became the most 
obvious choice in our planning. Today, even 
with the greater penetration of the 6800 and 
the announcement of the 6502 and the 
Z-80, the choice of the 8080 for the Heathkit 
H8 was still a good one. The 8080 still has 
sufficient computing power for nearly any 
hobby and personal computing application. 
But today with more choices available, the 
6800, Z-80 and 6502 are certainly viable 
alternatives. At some point in the decision 
making process, technical capabilities, speci- 
fications and other factors become meaning- 
less and the choice is made strictly on 
subjective or emotional grounds. 

What About the Others? 

What about all those other microproc- 
essors which are available to the hobby and 
personal computing user? Why shouldn't a 
hobbyist consider these devices as well? The 
answer is a difficult one. First the other 
microprocessors are certainly capable of 
producing the same or even improved per- 
formance over the most popular devices in 
use. However, since they have not been 
widely adopted by microcomputer manu- 
facturers, most of them are simply not 
available. 

2650 

The Signetics 2650 is a good example. 
This device was announced well after the 
8080 and 6800. However, it is a superior 
design in many ways. The 2650 is in effect 
more like a minicomputer than a micro- 
processor. It is extremely powerful in that 
it has a superior architecture and powerful 
instruction set. It also operates at a high 
rate of speed. Yet this device never really 
caught on. Today there are no widely used 
hobby and personal computers available 
using this device. As a result, there is limited 
software available for it. For the homebrew 
experimenter this device may be an excellent 
choice provided he is willing to develop his 
own hardware and support software. 

SC/MP 

The National SC/MP is another very 
interesting 8 bit microprocessor. It is per- 
haps one of the simplest and lowest cost 



NORTH STAR BASIC PROGRAMS 

HUNDREDS SOLD, EACH SYSTEM COMPLETE ON DISKETTE 
READY TO RUN. WORD PROCESSING, NORTH STAR TUTO- 
RIAL I, NORTH STAR TUTORIAL II (TEACHES NORTH STAR 
BASIC), ACCOUNTS PAYABLE, ACCOUNTS RECEIVABLE, 
PAYROLL, GENERAL LEDGER, MEDICAL-PROFESSIONAL, 
BILLING, SALES WITH SALES ANALYSIS AND GROSS PRO- 
FIT, INVENTORY, HISTOGRAM GENERATOR, COMPUTER 
CHESS, MAILING LABELS. $35.00 each. 

SOFTWARE LOCATER (LOCATE, INDEX-FREE SOFTWARE), 
CHECKBOOK BALANCING, BOWLING-GOLF HANDICAPPER, 
COIN COLLECTION INVENTORY, IMPORTANT DOCUMENT 
LOCATER, BUDGET PLANNER, GAME DISK. $25.00 each. 

IQ TESTER, COMPUTER MEMORY DIAGNOSTIC PERSONAL 
FINANCE, BUSINESS FINANCE, BIORHYTHM GENERATOR, 
DIET PLANNER, CRYTOGRAPHIC ENCODER, MATH TUTOR, 
A SORT UTILITY. $15.00 each. 

EQUIPMENT REQUIRED, SINGLE DRIVE, 8K FREE MEMORY, 
PRINTER OPTIONAL. 

TRS-80 LEVEL I & II (ON CASSETTE) STOCK MARKET ANALYSIS, 
GRAPHICS, TREND LINE ANALYSIS, BUSINESS APPLICATIONS. $15.00. 

BLANK DISKETTES $3.80 (UNDER TEN ORDERED, ADD $2.00 FOR 
SHIPPING; OVER TEN SHIPPED POSTPAID). 

CPM COMPATIBLE BASIC PROGRAM LISTINGS ALSO AVAILABLE. 



nm 



SOFTWARE 

DEPT. 11 P. O. BOX 2528 
ORANGE, CA 92669 







UOUDIDNTKNOW! 



OAE'S new PP-2708/16 
PROM Programnfier is the 
only programmer with all 
these features: 

• Converts a PROM memory 
socket to a table top pro- 
grammer: No complex inter- 
facing to wire — just plug it 
into a 2708 memory socket* 

• A short subroutine sends 
data over the address lines 
to program the PROM 

• Programs 2 PROMS for less 
than the cost of a personal- 
ity module. (2708s and TMS 
2716s) 

• Connect 2 or more in paral- 
lel — super for production 
programming 

• Complete with DC to DC 
switching inverter and 10 



' "Pat's Pending 



turn cermet trimmers (for 
precision pulse width and 
amplitude alignment) 

• All packaged in a handsome 
aluminum case 

PP-2708/16 . A & T $295. 

PP-2716 (Programs Intel's 
2716) A & T $295. 

OAE 

Oliver Advanced Engineering, Inc 

676 West Wilson Avenue 

Glendale, Calif. 91203 

(213) 240-0080 



Circle 291 on inquiry card. 



luly 1978 ©BYTE Publications Inc 135 



Circle 330 on inquiry card. 



Software 



Games • CRAPS (Las Vegas style) $6.00 
MULTIPIC LUNAR LANDER $8.00 
SLOT MACHINE $6.00 
GAME PACKAGE: Russian Roulette, Mad 
Scientist, and ABM $8.00 

Graplnics • PICTURE MAKER with AMP'L ANNY $12.00 
GRAPHICS PACKAGE 1: Laser Beam, Space 
SInuttle, and Blast Off $10.00 
GRAPHICS PACKAGE II: Rain in Greece, Flea, 
Textwriter, Random Walk $10.00 

Scientific • FOURIER FIT: Does curve fitting $15.00 

Systems • RANDOM NUMBER GENERATOR TEST $5.00 
HEX MEMORY LOADER $10.00 
MEMORY DUMP PROGRAM $10.00 
MEMORY SEARCH $5.00 

All Programs Written in BASIC 

Complete Easy to Read Documentation 

Programs Completely Tested 

SOFTWARE RECORDS 

P.O. BOX 8401-B 

UNIVERSAL CITY, CA 91608 

(cal residents add 6% sales tax) 



/DIGITALy JL 

RELIABILITY 

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CALIFORNIA RESIDENTS ADD 6% TAX 

y DIGITALy -TLy 



devices available. Because it is so simple it 
does not offer the computing power of the 
other devices. Nevertheless, it is extremely 
easy to learn and use. 

The main reason why the SC/MP has not 
been widely used is that again no hobby and 
personal computer manufacturer has selected 
it for its processor. National Semiconductor 
does provide several development kits that 
have found some interest in hobby and per- 
sonal computing fields. In addition, National 
has developed a BASIC-lii<e language called 
NIBL that was developed with the hobbyist 
in mind. For the homebrew enthusiast, the 
SC/MP is a good choice. 

1802 

The RCA 1802 is another interesting 8 
bit microprocessor. This is a CMOS device 
which has extremely low power dissipation. 
Its low power dissipation has led to incor- 
poration of the 1802 design into one well 
known experimenter's project, the next 
series of AMSAT radio amateur satellites. 
Again, no hobby and personal computer 
manufacturer has selected this as the pri- 
mary processor of a general purpose com- 
puter. The architecture and instruction set 
of the 1802 is peculiar and thus more diffi- 
cult to use than other devices. Little or no 
software is available. Nevertheless, the 1802 
is relatively easy to use and the homebrew 
hobbyist may find it a desirable choice. 
RCA makes several development kits that 
serve as a good starting point, one of which 
is intended as a low cost hobby computer. 

F8/3870 

The F8/3870 microprocessor is another 
widely used 8 bit microprocessor. The F8 
is effectively a two chip microprocessor 
featuring a ROM on one chip. The 3870 is 
MOSTEK's version of the Fairchild F8 in 
a single chip form. Neither of these devices 
has caught on for hobby and personal com- 
puter use. Only one hobby and personal 
computer manufacturer ever announced an 
F8 based machine and the company which 
manufactured it appears to be no longer in 
business. Both the F8 and the 3870 micro- 
processors were not designed for general 
purpose computer application. Instead, they 
were designed to be hardwired digital logic 
replacements. These are the microproc- 
essors that were designed to be buried inside 
of equipment as controllers. As a result they 
make very poor choices as general purpose 
digital computers. 

The same is true of the new Intel 8048/ 
8748. Like the F8 and 3870, the 8048 in- 
corporates all circuitry on one chip. This 
includes the processor, clock, both pro- 



136 luly 197g«>BYTE Publicdiions Jnc 



Circle 294 on inquiry card. 



CANADIANS! 

Introducing our kit-by-the-month 
plan available for only $500.00 down 
and $150.00 per month. 

(Write for more information) 

IMSAI 8080 KIT: $897.50 

ASSM: $1245.20 

Canadian Duty and Federal Tax Included 

Hobby systems from $999.00 (Kit). 
Business/engineering systems from 
$1 1 ,900.00. 
(Assembled and Installed*). 
Educational discounts available. We 
will develop custom application pack- 
ages. Contact us for further Informa- 
tion. Send $1.50 for catalogue. 

VISA • CHARGEX ACCEPTED 



Rotundra WML 
Cybernetics flMl 

Box 1448, Calgary, Alta. T2P 2H9 
Phone (403) 283-8076 

(Installation outside Western Canada extra}. 



SAVE $10.00 




I AST CHANCE to get the popu- 
lar OP-80A at the old $74.50 
price. Due to increasing costs, 
there will be a modest price in- 
crease (our first) in the OP-80A. 
Effective July 31 the price will 
be $84.50 Kit - $99.95 A & T. 

Oliver Advanced Engineering, Inc. 
676 W. Wilson Avenue 
Glendale, Calif. 91203 




ATTENTION MOTOROLA 
MEK6800D2 USERS 

4 Slot Card Rack 

Designed Speicifically for the 

MEK, MMS68104 MEMORY 

BOARD, EXORciser, and 

Micromodule Boards. 

Kit $64.95 
Assembled $79.95 

Check, Money Order, VISA or MC 

add $2.00 shipping, PA. residents 

add 6% sales tax. 

DEALER INQUIRY WELCOME 

PENTEC, INC. 

P.O. Box 148, Whitehall, PA. 18052 



Circle 309 on inquiry card. 



Circle 292 on inquiry card. 



Circle 299 on inquiry card. 



DIABLO 
TERMINALS ! 



LIMITED OFFER 

HYTYPE I TERMINAL 
$1595.00 

30 character per second 
Daisy wheel printer 
RS-232 serial interface 
Also: 

HyType II 
NEC Spinwriter 
Qume 

Sanders 12/7 
Centronics 
Univac 

Complete line of 
microcomputer products 




MICROCOMPUTERS, PERIPHERALS AND SOFTWARE 

101b Navarro San Antonio, TX 78205 512/222 142V 



Circle 231 on inquiry card. 



01 

c 
o 



o 



Engineers 

Hardware/Software 



Our clients are stepping up 
their engineering efforti 

Growth positions in the 15-40K 
range are available with manufac- 
turers of sophisticated systems. Di- 
verse areas include Graphic Arts. Text 
Handling Systems, Micro-Based Con- 
trollers, Manufacturing Systems, and 
Communications. 

HARDWARE - Design capability in 
TTLand CMOS Devices, Peripherals, 
and CPU. 

SOFTWARE - Real Time Operating 
Systems, Compilers, and Data Base 
Design - DOS. 

Call us at 603-888-5500 (collect) or 
send us vour resume - in confidence, 
of course. 

Touchstone Associates Inc. 

Engineering/EDP Mgt Consultants 
104 D,W. Hwv,, Nashua, N,H. 03060 



issC^s 



DAJEN/TELETEK 



MIC 



3<fC 



3< 



Dajen Electronics has merged 
with Teletek to provide greater 
customer service. We continue 
to offer the System Central 
Interface, and the Universal 
Cassette Recorder Interface. 
Call or write Ann Roberts for 
order and information. 



•sue 



ottc 



Teletek Enterprises, Inc. 

11505 B Douglas Road 

Rancho Cordova, Ca 95670 

916-351-0535 



Circle 371 on inquiry card. 



DISKETTES 

VERBATIM for Your DRIVE 



I Soft Sector 9I\ Afl 
10 Sector ^ i till 
16 Sector lliUU 

STANDARD $4 10^° 

Soft or Hard Sector ^. I W <" 



Ea. in 
boxes 
of 10 



in 

boxes 

10 



Circle 376 on inquiry card. 



CP/M1.4l,rsKTK^nn45 

PLASTIC BOX I°oVfkX? *3 

HAZELTINECRTISOOra^nOOO 

Complete 1»2«3 Computer »r< ir 
System: Hazeltine 1500, *3l40 
Horizon-2, Centronlc 779 

Visa, li/laster Charge, Cash, C.O.D. 



MANCHESTER EQUIPMENT CO., Inc. 

30MidlandAve.«Hicksville, N.Y.I 1801 
Call Collect: (516) 433-0613 



Circle 21 7 on inquiry card. 




USR-310 
ORIGINATE 
ACOUSTIC 
COUPLER 



operates With 

Any Standard Telephone 



Also Available 

USR 330 Origmate/AuloAnswer Modem 
USR-320 AutoAnswer Only Modem. 

(1 F C.C Certitied Package Connection to phone lines uia 
standard extension phone lach.) 

(2 Connection to phone lines via CBSIOOIF DAA which can be 
leased Irom phone company for approx SS.OO/mo. plus installation 
fee) 
INTERFACES: 

• USR 310 - RS232C only 

• USR 320 and USR 330 - RS232C and 20mA 

(Specify with order It both interfaces are required, add $10 to 
unit price ) 
ALL UNITS FEATURE; 

• 0-300 Baud Data Rate • Fully Assembled and 

• Stand Alone Unit Tested 

• Half/Full Duplex • Optional Annual 

• 90 Day Warranty Maintenance Coverage 
Prices include shipping and handling m conlmental U S Illinois 
Residents add 5% sales tax 

U.S. ROBOTICS. INC. 

Bo> 5502 ' Ctiicago Illinois 60<;80 ' (1121 528 9M5 



Circle 386 on inquiry card. 



BIT BASEMENT 

BARGAINS 

. SOROCIQ120 [assbled] ...$869.95/ 
j LEAR ADM-3A [assbled] ...$859. 95 1 

LEAR ADM-IA [assbled] ..$1199.95 
^16K RAM BOARD [assbled] $495.00/ 

250nS 180 day warranty 
f CENTRONICS 779 $1139.95' 

MICROPOLIS 1042 Mod I . $779.00 

BIT BASEMENT 

P.O. Box 1719 

Santa IVIonica. CA 90406 

H|(213) 322-9070 Q 

all items shipped FOB factory 



Circle 31 on inqyiry card. 



(a) 





(b) 



Digital Equipment Corporation, tine largest minicomputer company, 
introduced the LSI-i i microprocessor based single board computer to 
extend its minicomputer line downward into the microcomputer world. 
This PDP-i 1/03 system (a) is the DEC finished pacliage based on the LSI-I I. 
The Heath Company offers a version of the LSI-I J (b) which is called the 
HI J, which is available at lower cost in partial kit form along 
with extensive documentation aimed at the personal computer kit builder 
and experimenter. These photos are supplied by Digital Equipment Cor- 
poration and Heathkit, respectively. 



grammable and read only memory, as well 
as Input and output interfaces. The 8048 
was designed as a hardwired logic replace- 
ment and not for general purpose digital 
computer application. 

What About 12 and 16 Bit Microprocessors? 

Without question the trend in micro- 
processor development is toward larger, 
more sophisticated designs. While most 
microprocessor activity is centered around 
8 bit devices, there is clear evidence that 
single chip 16 bit microprocessors will 



eventually replace the 8 bit units. As semi- 
conductor technology improves, it will be 
just as easy to manufacture a 16 bit micro- 
processor as it is an 8 bit device. When that 
time comes, the price differential will be 
minimal. As a result, most purchasers of 
new equipment will go to the more powerful 
16 bit device over the 8 bit device, even 
though the computing power available is 
overkill for the application. 

There are a number of 16 bit micro- 
computers and one 12 bit device now on 
the market. In terms of overall microproc- 
essor usage, their popularity is small. But it 
is growing rapidly as more devices are 
developed. As these devices are incorporated 
in designs, the demand will go up and prices 
will decline. 

Some of the manufacturers making a 
16 bit microprocessor are given below. 

National Semiconductor PACE, 8900 
General Instrument 1600 
Data General microNOVA 
Digital Equipment Corp LSI-11 
Texas Instruments 9900 
Fairchild 9440 

At present there are few hobby and 
personal computers based on 16 bit micro- 
processors. Notably those that are available 
are the Heathkit H11 which is based on the 
popular DEC LSI-1 1 and the Technico 9900, 
based on the TMS-9900 part from Texas 
Instruments. 

The reason why 16 bit microprocessors 
haven't caught on in personal computing is 
that they have not been widely adopted 
elsewhere. The price is significantly higher 
than 8 bit devices and little or no software 
is available. 16 bit microprocessors are far 
more powerful and can process data much 
faster than an 8 bit microprocessor. How- 
ever, for most personal computing applica- 
tions such power is not necessary. 

At this time, the most widely used 16 
bit microcomputer is the DEC LSI-11. This 
particular computer has a wide following 
among hobbyists because of the great DEC 
software base. It is an ideal choice for the 
advanced user. 

None of the other available 16 bit micro- 
processors has yet caught on. The first 16 
bit microprocessor available was National 
Semiconductor's PACE. Despite its early 
lead, PACE never became popular. 

The newer Texas Instruments 9900 16 
bit microprocessor shows promise of becom- 
ing one of the more popular 16 bit micro- 
processors. This device may eventually be- 
come the 8080 of the 16 bit microproc- 
essors. This device is gaining acceptance in 
many areas. It is a powerful, general purpose 



138 luly 1978 ©BYTE Publicatiominc 



device. In addition, much of the software 
available for Texas Instruments minicom- 
puter line is compatible and could possibly 
be converted in the future for use on this 
device. Finally, Texas Instruments is one of 
the largest and most aggressive semicon- 
ductor manufacturers. They have the manu- 
facturing and marketing power to support 
and promote this device. Watch for it in 
future designs. 

The Micro NOVA is another very power- 
ful 16 bit microprocessor. It can effectively 
run all of the software available for the 
popular Data General NOVA line of mini- 
computers. However, this device like some 
of the others has not caught on. It is an ex- 
pensive device and not widely available. 
While the architecture is straightforward and 
easy to learn and the Data General software 
base is tremendous, it is doubtful that Data 
General will promote this device for the 
personal computing market or make such 
software available at competitive prices. 
(However, Data General is promoting the 
Micro-NOVA through selected retail stores 
and electronics distributions. Fairchild's 
9440 MPU uses the Data General architec- 
ture and will run the software. Although it 
is expensive, someone may eventually use 
the 9440 in a personal computer. 

The Intersil 6100 is a 12 bit CMOS micro- 
processor. Its claim to fame is that it has the 
architecture and instruction set of the 
famous DEC PDP-8/E minicomputer. It will 
also run software written for that machine. 
This gives the 6100 an excellent software 
base. But despite the software advantage the 
6100 hasn't caught on in personal com- 
puting. One reason is the high price as- 
sociated with 6100 based computers. These 
include Intersil's own Intercept series and a 
machine made by PCM. For the prices of 
these machines, a user can buy a used but 
real DEC PDP-8. In any case, the 6100 is 
a good chip with much potential. 

Summary and Conclusion 

The message in this article is relatively 
clear. If you are choosing a microcomputer 
for hobby and personal computer applica- 
tions, your best choice lies in the 8080, 
Z-80, 6800 or 6502 based machines. This is 
the mainstream of personal computing. The 
8080/Z-80 combination probably has the 
edge over all of these. The biggest question 
is who is going to make the 16 bit micro- 
processor. Will it be the new Intel 8086? or 
will Zilog's Z8000 win? We will have to wait 
and see. 

Finally, the message here is that "a proc- 
essor alone does not a computer system 




Another 16 bit minicomputer architec- 
ture available In microcomputer form Is the 
Data General Corporation's MicroNOVA 
shown here in a picture supplied by Data 
General. In the foreground is the processor 
chip standing alone; in back of the inte- 
grated circuit is a printed circuit board 
version of the computer Intended for use In 
dedicated applications. In the background 
can be seen the MicroNOVA fully inte- 
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stores and at several electronics distributors. 



make." When it comes right down to it, the 
type of processor is almost irrelevant to the 
user who is programming in BASIC or 
PASCAL or some other high level language. 
Overall, it is the software that gets the job 
done. If you base your choice of a personal 
computer system on the availability of good 
system and application software, you will 
not go wrong, whatever low level machine 
architecture is used." 



luly 1978 © BYTE Publications Inc 139 



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Continued from page 46 

The integrated circuit manufacturer can sell 
parts that would otherwise have to be 
thrown away, and the designer can buy state 
of the art parts for prices far below those of 
the equivalent 16 K part. 

The design task breaks down into the fol- 
lowing steps: 

1. Select the memory chip. For reasons 
stated earlier, the MK4115 (or equiva- 
lent) is the clear choice. 

2. Decide how to handle refresh. 

3. Analyze the timing requirements for 
the memory and the processor. 

4. Merge these two timing diagrams so 
that they work together. 

5. Design the circuitry. 

6. Lay out the circuit board. 

Refreshing Strategy 

When should you refresh? There are two 
types of refresh used in a dynamic memory 
system. Burst refresh suspends all other 
memory activity and quickly refreshes all 
the required locations at the top memory 
speed. This burst occurs once every refresh 
interval (generally every 2 ms). 

A preferable approach in a microproces- 
sor system is to use a distributed refresti 
approach, in which refresh cycles are inter- 
spersed with processor access cycles. In this 
manner the refreshing action is evenly spread 
over the 2 ms refresh interval. 

Let's examine some refresh alternatives: 

1. Use a 2 ms timer to interrupt the 
processor and tell it that the memory 
requires refresh. The processor inter- 
rupt routine then counts out the 
proper memory addresses and returns 
to normal processing. 

2. Use a timer with an interval of 2 ms 
divided by the number of required 
refresh cycles, and perform item 1 on 
a distributed basis. 

3. Interleave the refresh operation with 
normal processor timing: For example, 
notice (as the Z-80 designers did) that 
the processor address lines serve no 
useful purpose on the tail end of an 
instruction fetch cycle. During this 
time the processor must decode the 
instruction fetched from memory in 
anticipation of executing it. Why not 
put the refresh cycle (which needs 
the address lines) into this time slot? 

Items 1 and 2 above require processor 
overhead (processing time) since the inter- 
rupt system is used to provide programmed 
refresh. Of the two, the distributed approach 
is preferable because it produces less of a 
timing discontinuity in the background pro- 



140 luly 1978 (^ BYTE Publications Inc 



Circle 1 79 on inquiry card. 



Circle 120 on inquiry card. 



gram execution while the interrupt is being 
serviced. Item 3 is best in all respects, since 
no direct processor intervention is required 
to perform refresh. This is the so-called 
"transparent" or "invisible" refresh. This 
approach has already been implemented in 
some small system designs. It does, however, 
have some drawbacks in Altair (S-100) bus 
products. In examining the details of this 
approach, we'll describe an even better 
method of achieving "Altair (S-100) refresh." 
This discussion assumes an 8080 or equiva- 
lent processor. 

Catching the Bus 

The only time the processor can guaran- 
tee that the address bus is not needed is the 
second half of an instruction fetch cycle. 
This point in time is signified by the proc- 
essor control signal called Ml, which means 
"memory cycle one" of any instruction. 
Every instruction execution starts with an 
Ml memory cycle, in which the instruction 
is brought into the processor from memory. 
Depending on the instruction, further 
memory cycles might be required to finish 
execution of the instruction. During these 
subsequent cycles, the Ml signal is inactive. 
For example, the 8080 STA (store A) in- 
struction operates as follows: 

1. Ml: instruction word fetched from 

memory. 

2. M2: first half of the storing location 

read from memory. 

3. M3: second half of the storing loca- 

tion read from memory. 

4. M4: accumulator contents written 

into memory location specified 
by data brought in by steps 2 
and 3. 

The STA instruction is a 3 byte instruc- 
tion, and M2 and M3 are needed to read in 
the additional two bytes of the instruction. 
M4 does the actual execution of the instruc- 
tion, storing the accumulator. In this ex- 
ample, the Ml control signal is active only 
for step 1. The actual Ml cycle is divided 
into five processor cycles, called time states 
or "T-states." By the end of T3, the proc- 
essor has received the first byte of the in- 
struction and now requires two more time 
states, T4 and T5, to figure out what to do. 
This is the logical time to force a memory 
refresh (to be exact, T4 and T5 of Ml ). 

This is all very nice, but what happens 
when the processor is halted? During HALT, 
the signal needed to locate the point in time 
for refresh. Ml, is not there. In fact, most of 
the processor signals are not there. This is 
also true for processor RESET, wait states, 
and direct memory access cycles. This means 




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July 1978 ©BYTE Publications Inc 141 



Circle 405 on inquiry card. 



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that the design must do something special 
for these cases. 

What is really needed is an approach 
independent of processor control signals 
for refresh. The only signals on the Altair 
(S-100) bus that are present under all cir- 
cumstances (except power off) are the 
processor clock signals 01 and 02. 

Plan Ahead - Backwards 

Here's the plan: the memory design should 
contain a self-contained refresh system that 
uses only 02 for its operation. The control 
is arranged so that the memory is normally 
refreshing, and it is the exception cycle that 
diverts it away from refresh to perform a 
processor access. This emphasis is "back- 
wards" from most systems, which treat the 
refresh operation as the exceptional case. 
Now the card merrily refreshes itself until 
called on by the processor. If the processor 
"goes away," for example, in a prolonged 
wait state (a method frequently used to im- 
plement single-step and other front panel 
operations), the refresh continues. 

When the processor needs to access the 
memory card, it must do it on a synchro- 
nous basis. This means that the processor 
timing on a memory access into the dynamic 
memory card is designed to not jeopardize 
a refresh cycle in progress (it is synch- 
ronized with the refresh timing). Imagine 
the processor crashing in on a refresh cycle, 
and 64 data locations in the memory not 
being properly refreshed and going to 
indeterminate states. This is the kind of 
"soft error" that occurs only when you 
demonstrate the system ("It worked per- 
fectly on the bench. . ."), and promptly goes 
away when you try to fix it. 

Programmable IVIemory Timing 

Let's take a detailed look at the dynamic 
memory integrated circuit itself, and at 
exactly what signals are required to make it 
work. The integrated circuit described could 
be any of the various 16 K parts of the 
MOSTEK MK4116 type; or, with one small 
exception, any of the 4 K parts of the 
MK4027 type. 

Since 16 K is equal to 2^^, the part re- 
quires 14 address lines to uniquely select any 
of its cells. Allowing one line for DATA IN 
and another for DATA OUT, this adds up 
to all of the pins of the 16 pin package. 
That's fine if the chip doesn't require power 
supplies or read and write control, but un- 
fortunately, it does. This dilemma is solved 
by using a multiplexed address approach. 
Only seven pins are used for address inputs, 
and the address is loaded in two parts. One 



142 luly 1978 % BYTE Publicitions Inc 



Circle 388 on inquiry card. 



Circle 95 on inquiry card. 



of the big benefits of this approach is that, 
when the technology jumped from 4 K to 
16 K, an additional two address lines could 
be had with only one additional pin. On the 
4 K parts, this "unused" pin is a Chip 
Select input, which is used to select only one 
bank of parts that share the same output 
bus. As we'll see, the 16 K part does the 
chip select function without a chip select 
pin. 

Two control pins called RAS and CAS 
strobe the two 7 bit parts of an address 
into the memory part. These signals stand 
for Row Address Strobe and Column Ad- 
dress Strobe. They are active low signals, 
which means that they are normally at a 
high logic level, and are "strobed" by going 
into the low state momentarily. 

The sequence of events necessary for a 
memory cycle is as follows (see figure 3): 

1. Set up the low order 7 bit address on 
the address lines. This requires set- 
ting the address multiplexer to state 2 
(for example). 

2. Wait a suitable time for the address 
lines to settle. There will be a certain 
delay through the multiplexer, as well 
as some line settling time. 

3. Drop the row address strobe (RAS) 
to the low state. This latches the low 
address into the part. Both RAS and 
the column address strobe (CAS) 
start out high. 

4. Wait the "row address hold time," 
which specifies for how long after 
RAS drops the address lines must not 
change. This requirement is due to the 
setup time of the on-chip latches. 

5. Set up the high order 7 bit address on 
the address lines. This requires select- 
ing multiplexer state 3 (for example). 

6. Let the lines settle. 

7. Drop CAS to the low state. This 
latches the high address into the part. 
Don't remove the addresses until after 
the "column address hold time." 

When the logic level of the column address 
strobe drops, the output lines go from a high 
impedance state to a valid data state after 
the interval called "CAC" for Column 
ACess time. This is one way of specifying 
the access time of the memory part. 

These seven steps are the same for either 
a memory read or write cycle, the only dif- 
ference being the treatment of the RW pin 
which controls the choice of Read or Write 
operation. If this pin is held high throughout 
the cycle, a read operation is performed. To 
do a write, the RW pin is pulled low some- 
time after RAS. Exactly when it is pulled 
low determines whether the outputs become 
valid for the old data in the selected cell. 




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luly 1978©BVTePublicaIianslnc 143 



Circle 202 on inquiry card. 




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or whether they stay high impedance 
throughout the write operation. 

The chief difference between the 4 K and 
16 K part timing is in how the data outputs 
are treated when the column address strobe 
becomes inactive (high). In the 4 K part, 
the data outputs remain valid until the 
Column Address Strobe again makes a 
negative transition, in the 16 K part, they 
enter the high impedance state when the 
column address strobe goes high, effectively 
disconnecting the data output from the ex- 
ternal bus in a system. 

Maintaining Control 

There are several ways to control these 
strobe lines during refresh. The simplest 
way is to perform a full memory read cycle 
(row, then column address strobes) and not 
turn on the data input bus drivers; this does 
the refresh without affecting the external 
data bus. The problem with this method is 
that it is not the lowest power approach. 
Remember that for refresh only the row 
addresses (the least significant half of the 
address lines) are needed. The dynamic 
memory designers have provided for a 
mechanism called "RAS-only refresh" in 
the spec sheets, which consumes less power 
than a full row and column address cycle. 
In this method, the refresh counter address 
is applied to the address lines, and the row 
address strobe is made active (low voltage 
level). No other address bits or strobes are 
needed for this special refresh cycle. 

The chip select function in the 16 K 
memory is performed in effect by row and 
column address strobe timing (remember 
that the chip select pin was sacrificed for an 
additional address pin in the transition from 
4 K to 16 K). The method is quite simple: 
only those devices that receive both row and 
column address strobes in a memory cycle 
will activate their outputs; otherwise they 
will be in a high impedance condition. 
This means that it is possible to select one 
bank of programmable memories out of 
many whose outputs are tied together by 
(a) feeding a continuous row address strobe 
signal to all parts, and selectively feeding a 
column address strobe to only the selected 
bank, (b) the opposite (feeding a continuous 
column address strobe and selecting a bank 
with row address strobe), or (c) both (select- 
ing a bank with choice of column and row 
address). The manufacturers' literature fre- 
quently refers to this as "decoded RAS" 
or "decoded CAS." 

There is a slight power advantage to feed- 
ing the column address strobe to all devices 
and decoding the row address strobe to do 
bank selecting. However, a refresh cycle 



144 |uly 1978 © BYTE Publication! Inc 



Circle 76 on inquiry card. 



using ihe row address strobe only uses less 
power than a "RAS-CAS" refresh cycle 
using both strobes, as noted above. It turns 
out for logic simplicity (a real consideration 
in view of the small amount of Altair (S-1 00) 
bus card space available) that the decoded 
column address strobe method of selection 
is the optimum choice. It also happens to 
fit beautifully into the 8080 system timing. 
It is now apparent that the programmable 
memory address pins must be fed from three 
different sources: for a processor access, 
the low address half and high address half 
constitute two of the sources; and for re- 
fresh, the refresh counter address constitutes 
the third. To select these three groups of 
address lines, a TTL multiplexer (74153) 
may be used. This is a dual one-of-four 
selector that accepts four inputs and feeds 
a common output. The input which is 



selected depends on a 2 bit code (called the 
select bits) input to the multiplexer. These 
signals are labeled MUXI and MUX2 (see 
figure 4). For the 8 K part, which requires 
14 address lines, the multiplexer has to be 
seven bits "wide" so that the switching is 
done seven bits at a time. This means that 
three and one half 74153 integrated circuits 
are required. 

Processor Timing 

Turning our attention now to the 8080 
system control signals, the dynamic memory 
timing must be "dovetailed" into the 8080 
system timing. Figure 4 shows the timing for 
an 8080 fetch cycle. 

Lines 1 to 4 are control lines common to 
any 8080 system: the two clock signal in- 
puts 01 and 02, the address bus (actually 



o 
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© 





M I I I I M I I I I I I I I I I I I I I I I I I I I I I I I I I I 



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ADDRESS BUS 



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-SELECTED 



DATA INTO eoeo 7m'i)mtmnmmmmnmm^'^uo mmtmunKm 
s^N \ nm 

^ \ r 

©DATA OUT OP 8080 )(^XXXXYMXAAAXXXXXAXAXAAXX valid 

Figure 4: Master timing diagram lor on 8080 dynamic memory fetch cycle using the Altair 
(S-WOJ bus. Lines 1 thru 4 show the control lines common to all 8080 systems: the two clock 
signal inputs (<pl and <p2), the address bus and the processor SYNC output. Lines 5 and 6 are 
the control lines to a one-of-four multiplexer. Line 7 shows the state of the multiplexer selected 
by the two control signals IVIUXI and IVIUX2. Lines 8 and 9 are the row address strobe (RAS) 
and the column address strobe (CAS), respectively. Lines 10 and 11 show the processor timing 
requirements for accepting data read out of the memory. Line 12 is the write line (WL) from 
the 8080 used to enable a memory write into the programmable memory. 



July 1978SBYTEPubH[alionilni. 



145 



Circle 283 on inquiry card. 







t^vvfe 



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1976/1977 



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16 lines), and the processor SYNC output. 
Lines 5 and 6 show the control lines MUX2 
and MUX1 to a one-of-four multiplexer, and 
line 7 shows the state of the multiplexer 
selected by the two control signals IVIUX2 
and MUX1 . Lines 8 and 9 show the principle 
memory timing signals the row address 
strobe (RAS) and the column address 
strobe (CAS); lines 10 and 1 1 show the proc- 
essor timing requirements for accepting data 
read out of the programmable memory. 
The "valid" indication on the waveform of 
line 10 shows when the eight data lines into 
the processor must be stable for a success- 
ful memory read. The DBIN signal (line 11) 
is a signal issued by the 8080 to notify the 
input buffers to turn on in preparation for 
receiving input data. Line 12 shows the write 
line (WR) from the 8080 which is used to 
enable the write operation into the memory. 

Working Together 

Lines 5 thru 9 of figure 4 constitute the 
actual memory system design, the result of 
trading off memory, Altair (S-100) bus 
and processor parameters, and verifying that 
all the processor and memory timing con- 
siderations are met. The ultimate criterion of 
a good design is that it can pass a "worst 
case" analysis — every specification for the 
8080 and the programmable memory can 
be the worst specified in the data sheets, 
and the system will still work. In fact, a 
good figure of merit for a digital design in- 
volving complex timing (such as this one) is 
how far beyond worst case the specifications 
can be for the system to still function 
properly. This is known as margin. The 
better the margin, the better the designer 
sleeps at night, and the better guarantee that 
the system will work over a long production 
run. 

Notice the similarity between 02 and 
RAS (lines 2 and 8) of figure 4. RAS is 
simply 4>2 with certain positive parts missing. 
Whenever the 8080 starts an instruction 
fetch cycle (signalled by SYNC), the RAS 
line must make its negative transition dur- 
ing MUX state 2 and stay there throughout 
the memory cycle. If the 02 pulse during 
T2 were allowed through, the memory tim- 
ing requirements would not be met. To 
inhibit this 02 pulse, SYNC is delayed 
slightly and used to gate off the unwanted 
part of 02. Notice that this gating signal is 
MUX1 (line 6). SYNC is delayed very simply 
by feeding SYNC to the D input of a flip 
flop and clocking the flip flop with the lead- 
ing edge of 01 . 

Before this cycle gets underway with row 
address strobe line RAS dropping, the 
address lines to the memory must be set up 



146 (uly 1978 6 BYTE Publicitionsinc 



Circle 318 on inquiry card. 



to receive the low order part of address lines 
from the processor. The multiplexer must 
therefore switch from state (the refresh 
select state) to state 2 (processor-low address 
state) prior to the fall of RAS. This is 
accomplished by the signal IVIUX2, which is 
turned on by the leading edge of SYNC. 
This edge gives the address lines more than 
enough time to settle before they are sampled 
by RAS. 

After the row address strobe part of the 
cycle is satisfied, the multiplexer switches 
to state 3 (the other half of the processor 
address lines), and column address strobe is 
activated. The column address strobe line 
goes low when three signals are asserted as 
follows: 

1. 02 high. 

2. MUX1 high. 

3. The bank of programmable memories 
is selected. 

The third control, often called "this mem- 
ory," performs the chip select function by 
feeding the column address strobe to only 
one bank of programmable memories at a 
time. 

Looking now at lines 9 and 10 of figure 
4, we can calculate the access time margin 
of the memory system. The data out of the 
programmable memory becomes valid some- 
time after CAS makes its negative transition. 
The data into the processor must be stable 
and valid at the time shown in line 10. 
Counting the time from CAS-low to the 
earliest time data must be valid, the pro- 
grammable memory access time should be 
6X55 ns (each division is 55 ns), or 330 ns. 
In a system, this time is reduced by approxi- 
mately 50 ns to allow for the delays through 
the data buffers and line settling time. 
Let us say that the CAS to data access time 
(CAC) must be 330-50 or 280 ns. The speci- 
fication for the slowest IVIK4n5 gives a 
maximum t^;\c °f ^^^ "5' ^ ^^''y comfort- 
able margin. (If the margin point seems 
to be overstressed, its importance will be 
seen in the section on Altair (S-100) bus 
compatibility). 

To complete the cycle, the CAS line 
must be held low until the processor is 
definitely through with the data lines. This 
is indirectly specified in the 8080 data sheet 
as being the time that DBIN goes high. Since 
this point is anywhere from 25 to 140 ns 
after the rising edge of 02 in T3, the CAS 
line is held low until the falling edge of 02 
in T3. Note that the RAS line makes its low- 
to-high transition well in advance of CAS's 
going from low to high. This is permitted in 
the newer dynamic memory parts but would 
not be acceptable in the older ones, such 



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July 1978 Q BYTE PuWicilionsInc 147 



80 percent of dynamic 

memory design is printed 

circuit board layout. 



as the MK4096 dynamic 4 K (both column 
and row address strobes had to go high 
together). By the time the RAS line makes 
its next negative transition, the multiplexer 
has switched back to state 0, selecting the 
refresh address, and another refresh cycle 
begins. 

The processor access cycle chain of 
events is initiated by the 8080 SYNC signal. 
Anytime the SYNC signal is not there, the 
circuitry automatically reverts to refresh 
operation. (Multiplexer state selects the 
refresh counter, the RAS line continuously 
cycles, and the CAS line remains inactive 
(high) for the RAS-only refresh operation.) 
This implements a strategy that maintains 
refresh on a fail-safe basis. 

The refresh counter is clocked by a signal 
which is suppressed during a processor access 
cycle, so that none of the refresh addresses 
is skipped. A refinement detail of the de- 
sign is a flip flop which eliminates some of 
the redundant refresh cycles to conserve 
power. This is possible because the latter 
scheme considerably "over-refreshes" the 
memory, since a full 128 row refresh is per- 
formed in much less time than the 2 ms the 
specification calls for. Refreshing more 
frequently than the specification requires 
has no effect on proper memory operation. 

For a write operation, the 8080's write 
line (WR) is timed such that it can be fed 
unmodified to the memory's read or write 
control (RW) pin. The write operation is 



RAS 

£55 




RAS/CAS CYCLE 








LONG RAS/CAS CYCLE 








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50 NANOSECONDS / DIVISON 



Figure 5: Supply current waveforms for the MOSTEK MK4116 16 K 
dynamic memory (courtesy MOSTEK). 



terminated by the WR line going low to 
high, or the CAS line going low to high, 
whichever occurs first. 

Now, the Hard Part 

You might think that the design is com- 
plete when the final schematic is drawn. 
Not so: it is about half complete. As any 
dynamic memory system designer will tell 
you, 80 percent of dynamic memory design 
is printed circuit board iayout. These parts 
don't just sit there like their static counter- 
parts, responding with data whenever ad- 
dressed. The dynamic part is actually a 
sophisticated analog part inside, aside from 
being a dense memory array. The circuitry 
that senses the charge on the storage capaci- 
tors must resolve millivolt levels in the 
presence of continuously running 12 V 
clocks. The power distribution system and 
power supply noise decoupling are therefore 
the most critical elements of a good dynamic 
memory design. This consideration has 
killed more dynamic designs than any 
amount of poor circuit design. 

The dynamic memory has four power 
pins; 12 V, 5 V, ground and -5 V. The 5 V 
supply is connected only to the output 
transistors (to provide TTL compatible 
outputs), and draws next to nothing in 
power. The —5 V supply provides high 
current ptz/jes of very short durations. Since 
these pulses are bipolar in nature, the actual 
DC current for the —5 V supply is also very 
low. It is the 12 V supply and ground system 
that need special layout consideration. 

The four power pins are located on the 
four corners of the dual in line package, 
which somewhat simplifies a good power 
distribution layout. The best layout for 
power is one in which all power pins are fed 
from a horizontal and a vertical direction. 
This is known as "gridded" power distribu- 
tion, since each power pin is placed at the 
intersection of a grid of power lines that 
simulates a plane surface. Wherever possible, 
the power lines should be as wide as the 
array density will allow. When density con- 
siderations prohibit wide power buses on 
all four supplies, the 5 V and —5 V supply 
buses can be fed with smaller traces (but 
should still be gridded). 

The second important consideration is 
power supply bypassing. The current drawn 
by the 1V1K4116 is shown in the waveforms 
of figure 5. Notice that all the current is 
drawn as a result of RAS and CAS transi- 
tions. The factor which sets the MOSTEK 
4116 apart from all other 16 K devices is 
that after the RAS and CAS current de- 
mands, the Iqq (12 V current) drops to 
nearly 0. The fact that other parts drop to 
some continuous current (on the order of 



148 July 1978 ©BYTE PuWiclIions Inc 



20 mA) when the RAS line and CAS line are 
inactive (high) accounts for the wide dif- 
ference in power dissipation between the 
MK4n6 and the others. MOSTEK does it 
by turning off the sense amplifiers when 
they are not needed, and the rest of the 
semiconductor world is presently designing 
(or redesigning) to duplicate this feature. 

Looking at the most critical current 
waveform of figure 5, Iqq, it is seen that 
the instantaneous current drawn is about 
100 mA maximum. TOO mA per device 
times 32 devices (in a 32 K memory com- 
prised of 8 K parts) is 3.2 A at 12 V. Before 
running out to buy a water pump to cool the 
12 V regulator, notice that the 100 m A 
is drawn for only a very brief time. Suppose 
you connect a capacitor between 12 V and 
ground, let it charge up during the low cur- 
rent demand time and supply the instanta- 
neous current pulses when needed. This is 
the role of the so-called "bypass" or "de- 
coupling" capacitors. The value needed for 
these capacitors can be readily calculated by 
estimating the area under the curves in 
figure 5. Using the formula C=(iAt)/Av, the 
capacitance can be calculated for any 
allowed drop in the 12 V supply (Av). The 
MK4116 allows a 10 percent tolerance on 
all supplies, so a good conservative number 
to use for the 12 V supply is about 2 percent 
or 0.24 V. Estimating iAt (the area under 
one of the current waveforms) from figure 5 
to be about 50 ns times 1 00 mA, the formula 
yields a value for C of approximately 
0.02 /jF. (0.1 /iF capacitors should work 
fine.) 

The reason for the above exercise is that 
even though the data sheets may say so, 
not all dynamic memories are identical. 
The primary difference between today's 
dynamic memories is in the current wave- 
forms, and only two manufacturers (MOS- 
TEK and Intel) even publish them. 

For the bypass capacitors to be effective, 
they must be located as close to the memory 
power pins as possible, so that the inductance 
of the printed wire feeding the instanta- 
neous current to the part does not interfere 
with this current supply. Note that for 
exactly the same considerations as the 12 V 
supply, the —5 V supply should be ade- 
quately "bypassed" with capacitors. The 
bypass capacitors should be evenly dis- 
tributed throughout the memory array. 

An often neglected detail of dynamic 
memory layout is that the ground system 
between the address line drivers and the 
memory array must be very heavy. As the 
number of integrated circuits in the memory 
array increases, the requirements on the 



address line drivers become more stringent. 
Each address pin contributes a capacitance 
of about 4 picofarads, and they are all tied 
together in the array. If you follow any 
address line through a printed circuit board 
memory array, you'll see that it takes a 
rather long and usually discontinuous path. 
For this reason, series damping resistors 
should be placed between the address 
buffers and the memory array to help damp 
out the undershoot and overshoot caused by 
the layout discontinuities. 

It is quite a trick to achieve optimum 
power distribution layout on an Altair 
(S-100) bus format card. The system ground 
pin comes in at only one corner of the card, 
and it must be routed in a "web" for a good 
board level ground distribution. Additionally, 
the required on board regulators use up a 
lot of space which, along with the permis- 
sible heat dissipation, puts an upper limit on 
the number of chips that can exist on a 
card. The message here is that a good memory 
design requires extreme cooperation be- 
tween the designer and the printed circuit 
board layout person. 

Ah, That "Altair (S-100) Compatibility" 

If you have plowed your way through the 
timing diagrams and technical discussion 
of this article, you can now appreciate the 
fact that the question, "Is it Altair (S-100) 
bus compatible?" is one that cannot be 
answered with an unqualified yes or no. 
The memory system is designed to be 
Altair (S-100) bus compatible, but when you 
plug it into a Stromdecker X-3 mainframe, 
running a Fantastroid Z-SOQ processor 
card with memory-managed-phantom- 
indirect-parabolic-vectored-restart imple- 
mented, it might not work. The design 
philosophy is to use as few of the Altair 
(S-lOO) signals as possible, to account for 
unforeseen variations in various systems. 
Back to figure 4; the only timing lines 
the memory counts on being there are 
(?il, 02, SYNC, DBIN (actually MEMR, 
memory read) and WR (actually memory 
write). In the case of the memory write 
line, any Altair (S-100) design should 
derive the memory write signal from SOUT 
and WR, since early designs put the gate to 
do this on the front panel board, and you 
therefore cannot guarantee that the signal 
MEMW will be there in all systems. 

Some analysis of the interlocked timing 
of figure 4 reveals that the card will work 
with any implementation of 01 and 02 
that meets the 8080 specifications. The 01 
and 02 timing shown in figure 4 is that 



luly 1978©BYT[ Publications Inc 149 



Imagine pulling out four 

8 K static memory cards 

and plugging in a single 

32 K card that uses less 

power than one of the 8 K 

cards. This can be done 

with today's dynamic 

memories. 



provided by systems using an 8224 
clock generator with an 18 MHz crystal; 
this is the most popular Altair (S-100) 
implementation. Will it work with Z-80 
processor cards? Maybe. The Z-80 requires 
only a single clock, has no SYNC output, 
and times its read and write operations 
slightly differently than the 8080. Designers 
of Z-80 based Altair (S-100) cards realize 
that there is a big compatible world out 
there that they must back into, so they 
attempt to synthesize 8080-type signals 
out of the Z-80 system timing. How suc- 
cessfully they emulate the 8080 (meaning 
how accurately they reproduce signals such 
as 01, </)2 and SYNC) determines the degree 
of compatibility in a system of Altair 
(S-100) cards. 

Incidentally, a final look at figure 4 illus- 
trates the elusiveness of the memory "access 
time" specification. How many times have 
you seen ads that say something like "300 ns 
memories," and wondered what this actually 
means in an 8080 system? Figure 4 shows 
that the access time is not itself a figure of 
merit. The actual memory timing must be 
compared with the system timing require- 
ments to make any sense. The general idea 
in a dynamic memory design is to crowd the 
multiplexing of row and column address 
strobe events as close as possible to the 
processor addresses becoming valid, so that 
the maximum memory access time is allow- 
able. One thing /5 certain — faster memories 
always cost more than slow ones, so a cost 
effective design should accommodate the 



slowest available. The access time margin is 
so wide in figure 4 that the system could 
actually run much faster and still retain 
comfortable margins. 

Final Thoughts 

The design presented here is intended 
primarily to show the important areas of 
consideration in a dynamic memory design. 
The general concepts can be applied to any 
processor and memory interface, using the 
same methodology of carefully analyzing 
the specific timing requirements of the sys- 
tem and the programmable memory com- 
ponents, and then merging the two together. 
Exactly how this is done is the exciting part 
of digital design, where the designer can be 
creative. It is most important to first examine 
the system requirements and keep the 
memory faithful to these specifications. 

A dynamic design pays handsome divi- 
dends in a system. By using low power 
Schottky TTL (74LS family), the 5 V cur- 
rent requirement is kept so low that the 5 V 
regulator on the card does not even need a 
heat sink. The 12 V regulator requires a 
modest heat sink. The total power require- 
ment of the board can be generally less 
than any static board, regardless of density. 
Imagine pulling out four 8 K static cards and 
plugging in a single 32 K card which uses 
less power than one of the 8 K cards. This 
type of performance is possible only 
with today's high performance dynamic 
memories." 



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"THE ORIGINAL " 

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78 



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BYTE 



Circle 302 on inquiry card. 



BYTE July 1978 151 



Ted Williams 
Steve Conley 
Dept of EE 
University of Arizona 
Tucson AZ 85721 



A High Level Language 



for 8 Bit Machines 



i Assignment 

A. VAR =exp 

II Branch 

A. IF ^ VAR relation exp 



B. ENDIF 



III Loop 

A. DO 

B. UNTIL (3 VAR relation exp 

C. ENDDO 

IV Subroutine 

A. CALL (3 NAME 

B. SUBROUTINE NAME 

C. RETURN 

V Input and Output 

A. READ /3 channel, VAR1, VAR2, 



B. PRINT (3 channel, ( VAR 
1 quotes 



VI Leaving Interpreter 
EXIT 



Variable VAR is set to the value of 
the expression on the right side of 
the equal sign. 



The code following, up to the cor- 
responding ENDIF, is executed only 
if the variable value satisfies the 
relation. 

Indicates the portion of code to be 
executed if the earlier IF statement is 
satisfied. 



The code between a DO and an 
ENDDO is executed repetitively until 
the variable satisfies the inequality. 
More than one UNTIL may be 
included in one DO loop. 



A CALL executes the code following 
the SUBROUTINE statement with 
the same name until a RETURN is 
encountered. 



READ specifies a transfer from the 
device specified by channel, conver- 
sion to floating point, and transfer to 
the locations in memory specified by 
the variable names. 

PRINT sends data to a specified out- 
put device in binary coded decimal 
form, prints ASCII code between 
quotes, and sends a carriage return 
for each "!". 



Causes the interpreter to return to 
the monitor. 



Interpreters such as BASIC or APL do 
not translate the high level source code into 
machine language. Rather, they scan the line 
of code and then perform a set of operations 
based upon the instruction and data stored 
in tables from previous instructions. Thus an 
interpreter saves the time consumed by 
translation, but no machine code is saved for 
later execution. The main advantage of an 
interpreter is the ease of error correction. 
The results of each line of code can be 
printed and the exact source of difficulty 
can be pinpointed. The price paid for this 
feature is memory. The source code, data, 
tables and the Interpreter program must all 
be resident in memory at the same time. 



Tab/e J: The interpreter instruction set 
allows the evaluation of expressions, condi- 
tional branches, loops, subroutine calls with 
multiple returns, and 10 instructions. Key- 
words are indicated by boldface type in this 
table. The variable names must contain six 
or less alphanumeric characters and start 
with a letter. Expressions (exp) may contain 
numbers, operators, variables, functions and 
parentheses. Any of the following relations 
may be used: >, > = , < , < =, =, > < . |3 
indicates mandatory space. All other spaces 
are ignored by the interpreter. The only 
limit to the number of loops that may be 
nested is the amount of memory space 
available for storage on the stack. Everything 
past a semicolon on a line will be ignored as 
a comment. Each statement must be 
terminated with a carriage return. 



152 July 1978eBYTE Publications Inc 



Programs also run slower because the code 
within loops must be reinterpreted on each 
pass. 

The language proposed here is suitable for 
use with both an interpreter and a compiler. 
If both are available then the time con- 
suming process of compiling is avoided until 
permanent machine level code is required; 
furthermore, the debugging of a developing 
program may be done quickly and easily 
with an interpreter in an interactive mode. 

The purpose of this article is to intro- 
duce readers to concept interpreters and to 
present an example of an interpreter for a 
high level language. 

The interpreter instruction set is shown in 
table 1. In addition to evaluating expres- 
sions, the interpreter can also perform condi- 
tional branches, loops, subroutine calls with 
multiple returns, and 10 instructions. These 
instructions are sufficient to execute very 
complex tasks. In fact, the language is 
devised to encourage a top down approach 
to writing code so that it is easy to under- 
stand, debug and modify. More complex 
groupings such as an IF THEN ELSE con- 
struction might yield slightly shorter pro- 
grams if included in the language, but the 
convenience of using such structures does 
not seem to warrant the considerable effort 
required for implementation. Good program- 
ming techniques are essential to useful code. 

Some other simplifications are made just 
to simplify this interpreter. No integer vari- 
ables, arrays, complex variables or double 
precision variables are included. All numbers 
are considered to be floating point numbers 
with a 4 byte mantissa and a 1 byte ex- 
ponent. Also the subroutine calls do not pass 
arguments. Since all the variables are global 
symbols, local variable names within a sub- 
routine may not duplicate those in another 
routine. These restrictions are made so that 
the code for the interpreter would fit on a 
small machine and so that the main features 
of the interpreter will not be obscured. 

The interpreter program is written in 
terms of a universal set of instructions, 
MACL1. These macroinstructions can be 
translated into machine code instructions for 
a variety of microprocessors if the expan- 
sions for each macroinstruction are defined 
for your microprocessor. The translation of 
the interpreter into machine code is simpli- 
fied by the use of a program called a 
macroprocessor. Otherwise it can be done by 
hand. 



High Level Language Statements 

AREA=0 

X=1 

Y = (Xt2) -^ (2*X)-i-3 

DELTX=0.1 

IND=11 



Notes 



initialization 



DO 



X=IND*0.1 

YPLUS=(Xt2)+(2*X)+3 I 

AREA=AREA+DELTX* (YPLUS+Y)»0.5 / 
UNTIL IND>=100 

IND=IND+1 



ENDDO 

PRINT 1, "The area is", AREA 

EXIT 
END 



loop condition counter is 
"IND" 

start of DO loop 



; sum areas using trapezoi- 
dal integration rule 

UNTIL evaluates loop re- 
iteration condition 



ENDDO tests loop reitera- 
tion condition 

output message and AREA 
through channel 1 

go back to monitor 



Listing 1: This example program, written in the high level language 
of this interpreter, is a trapezoidal integration routine for the function 
Y=(X\2)+(2*X) 3. 



P2=3.14159»0.005 



READ 2,A 




IF 


A<SIN (P2) 

PRINT 1, A "A IS TOO SMALL 

EXIT 

ENDIF 


IF 


A>SIN(100*P2) 

PRINT 1,A, "A IS TOO BIG",! 

EXIT 

ENDIF 


LOW=1 




Hl = 100 




DO 


UNTIL HI<=LOW+1 
IVIID=INT( (HIH-LOW) 12) 
IF A>SIN(P2*IVIID) 




Hi=MID 
ENDIF 




IF A>SIN(P2*MID) 




LOW=MID 
ENDIF 


ENDDO 




IF a=sin(p: 


l*LOW) 
HI = LOW 
ENDIF 


IF A=SIN(P2 


!*HI) 
LOW=HI 
ENDIF 


XL0W=SIN(P2*L0W) 


XHI=SIN(P2 


♦HI) 


PRINT1,XLOW,XHI,A 


EXIT 




END 





Listing 2: This example 
program gives the flavor of 
a longer program with 
references to various 
mathematical routines. In- 
dentation is done to 
emphasize program 
structure. 



luly 1978©BYTE Publicaliom Inc 153 



The following sections discuss the im- 
plementation of each of the five types of 
instructions and show the function of the 
instructions in flowchart form. Two exam- 
ples shown in listings 1 and 2 illustrate the 
simplicity of the resulting high level 
language. 

Interpreter Organization 

The basic elements of the interpreter and 
the utilization of memory are shown in 
figure 1. Besides the source code and the 
interpreter routines, there are four tables, 
two stacks and a workspace for control 
pointers. The workspace is used for pointers 
to keep track of positions in the various 
tables, limiting addresses for the tables, 
scratch area for temporary results, and ad- 
dresses for 10 channels. 

The stacks are used for saving subroutine 



return addresses and for evaluating equations 
as described in our discussion of the assign- 
ment operations section. The four tables are 
for remembering: 

1. where previously defined variables are 
stored. 

2. where subroutines are located in the 
source code. 

3. where subroutines are located in the 
interpreter code. 

4. the location of routines to perform the 
operations (+, — , *, /, t) and functions 
defined for this language. 

The tables are searched by a linear search 
routine which starts with the portion of the 
table most likely to contain the item. The 
ASCII byte string in the name list is com- 
pared with the desired name. The end of a 
name or symbol in the table is denoted by a 



CODE TO BE INTERPRETED 



CONTROL POINTERS 




INTERPRETER 



STATEMENT 
EVALUATION 

















SEMANTIC LOOKUP 


i TABLE 




C 




R 




F 




I 






A 




^ 




V 




F 






1 




T 




A 










L 




u 

R 
N 




L 






TOKEN 




f 




f 




f 




t 


POINTER 



POINTER 


SEMANTIC 






• 


PLOT 






^~— • 


DONE 











EXPRESSION 
EVALUATION 




SYMBOL VALUE 
TABLE 



TOKEN 


POINTER 






NYSM 


• 






X 


•- 








>| 


i 


1 







p 







E S 




P s 


R T 




E T 


A A 
T C 
K 
R 




R A 
A C 
N K 
D 



TOKEN 


POINTER 






* 


» ' 






SIN 


• -^ 







Figure 1 : A map detailing ttie utilization of memory by the Interpreter. Part of the memory consists of four tables that are used 
to look up values of previously used variables, locations of subroutines in source code, locations of machine language subroutines 
for the interpreter, and locations of routines for symbols and functions defined by the Interpreter. The two stacks are used in 
the parsing of equations and when a subroutine is called or returned from. The two largest areas of memory contain the source 
code and actual machine code for the Interpreter. 



154 



July l97g©BYTEPublicj|iam Inc 



one in the most significant bit, called a 
terminator. When a terminator is reached in 
the name list, the pointer in the cor- 
responding address table or value table is 
incremented to the next item. When a name 
is found, the pointer in the corresponding 
list points to the location where the value 
for the symbols table or the address is 
located. The desired name or symbol is 
always added to the list to make sure that 
the search does not run off the end of the 
table. After the search, the name pointer can 
be checked to see if the search went beyond 
the current length of the list. This technique 
is faster than putting an end check into the 
search routine. 

The subroutines in the high level source 
code are not the same as the routines used 
by the interpreter for performing operations 
and functions. The first set of subroutines 
contain source code and the second set 
contain machine code for operations exe- 
cuted by the interpreter. 



Operation 



.JSR 



.JSR 

.POP 
.MOV 

.JSR 



Operand 



Igvarad 



level 



wdeval 

(wptr), 
wdeval 

Ifinstm 



Description 

Get variable address. Use current line pointer to 
fetch variable name. See if name is in name table. 
If it is, transfer its address to (wptr). If it is not, add 
name to table. Transfer symbol address from symbol 
value pointer to workspace at (wptr). Update the 
line pointer up to the equal sign. 

Subroutine EVAL evaluates the right side of the 
expression and returns the value on the stack. 

Put result from EVAL call into workspace. 

Transfer the result from EVAL call to the location 
specified by the contents of (wptr). 

Scan the rest of the line of code skipping over the 
comment field up to the carriage return and update 
the current line pointer. 



Table 2: An outline of the EQN routine. The routine first gets the variable 
address, then evaluates the right side of the expression and puts the value into 
the workspace. It then skips over the comment field to the carriage return, 
updates the line pointer, and decodes the next line of code. This outline flows 
from top to bottom, with the "operations" and "operands" intended to be 
used with a macroassembler. 



Interpreter Operation 

Initialize: The initialize portion of the 
interpreter has two functions. It loads the 
source code from a peripheral and it ini- 
tializes the workspace. As it loads, it also 
scans the source code looking for subroutine 
statements. The name of each subroutine is 
put into the subroutine name table, and the 
corresponding position in the code is put 
into the subroutine address lookup table 
shown in figure 1. The initialize routine is 
entered from the system monitor, and the 
initialize routine returns control to the 
system monitor. 

Scan: The scan portion of the interpreter 
receives control from the monitor and scans 
the code starting from the current contents 
of the line pointer. Depending upon which 
of the 12 instructions of table 1 is encoun- 
tered, this routine jumps to one of the 
routines as shown in figure 1 in order to 
execute one line of code. If an end of file 
(EOF) character or an error is encountered, 
the scan routine transfers back to the moni- 
tor for text editing, reloading or further 
execution. 

A trace option is included in the scan 
routine which prints the name and value of 
all assignment statements as they are exe- 
cuted. This option is included for debugging 
and tutorial purposes. 

Assignments: If the scan routine detects 
an assignment statement then the interpreter 
jumps to the EQN routine of figure 2. The 
EQN routine operation is outlined in table 2 
as a list of operations and operands. 

The EQN routine uses the routine EVAL 



LI mode: In this mode an operand, unary operator, left parenthesis, or function is 
expected. 



If this token 
type is 
received 


Then perform operation 


operand: 


stack the operand. If the operator stacked is not a "(", 
perform the indicated binary operation. Proceed to 
mode L2. 


operator: 


must be unary. Stack operator and stay in mode LI . 
Push a onto the stack if operator is a minus sign. 


function: 


push variable near operand stack. Push $ onto opera- 
tor stack to indicate a function. Stay in mode LI . 


right 
parenthesis: 


error. 


left 
parenthesis: 


push it onto operator stack. Stay in mode LI . 



L2 mode: In this mode an operator, right parenthesis, or carriage return is expected. 



If this token 
type is 
received 


Then perform this operation 


operator: 


push operator onto stack. Go go mode LI . 


operand: 


error. 


left 
parenthesis: 


error. 


right 
parenthesis: 


pull operator from stack. If it is a "(" unstack it and 
return to mode L2. If it is a $ perform the function, 
then return to unstack operation. 


carriage 
return: 


check operator state. Operand stack should have 
exactly one value. Convert value to floating point. 
Return to EQN routine. 



Table 3: The Bauer-Samelson algorithm to determine the order of operation 
of an expression. The algorithm starts in the LI mode looking for an operand. 
The execution of the expression starts in the Innermost parenthesis and works 
from left to right without any consideration for precedence. 



July 1978 © BYTE Publicitions Inc 1 55 



( EVAL j 



PUSH - 
ONTO 

OPERATOR 
STACK 



-® 



GET 
NEXT 

CHARACTER 



PUSH'( 
ONTO 

OPERATOR 
STACK 



PUSH '0 
ONTO 
OPERAND 
STACK 



PUSH - 

ONTO 

OPERATOR 

STACK 




OUTPUT 
ERROR I 



( RETURN j 



CONVERT 
NUMBER 
TO BINARY 
FLOATING 
POINT 



GET 

NEXT 

CHARACTER 




PUSH 

OPERATOR 

ONTO 

OPERATOR 

STACK 



-hS) 



PULL NEXT 

CHARACTER 

OFF 

OPERATOR 

STACK 



PULL NEXT 

CHARACTER 

FROM 

OPERAND 

STACK 



OUTPUT 
ERROR 5 




OUTPUT 
ERROR 3 



( RETURN ) 




Explanation of error messages used in this flowchart 


Error 1 : 


An operand, "(", or unary operator ex- 




pected at this point. 


Error 2: 


Variable name exceeds six characters. 


Error 3: 


An operator, ")", or terminator expected 




at this point. 


Error 4: 


A left parenthesis not found to balance 




this right parenthesis. 


Error 5: 


A carriage return was encountered pre- 




maturely. Check for missing right 




parenthesis. 





OUTPUT 
ERROR 2 






( RETURN ) 



CONVERT 
VARIABLE 
TO NUMBER 
ON OPERAND 
STACK 



Figure 2: Flowchart of the modified Bauer- 
Samelson algorithm. The table of error 
messages summarizes all the errors that may 
be encountered while an expression is being 
evaluated. For an algorithmic explanation 
of the flowchart see table 3. 



PULL 
FUNCTION 
NAME OFF 
OPERAND 
STACK 



DO FUNCTION 



OUTPUT 
ERROR 4 



( RETURN ) 



( RETURN ) 



156 



)ulv 1978 ©BYTE Publlcitiom Inc 



Equation: X = +4.t VAR (CR) 



Present 


Character 


New Operand 


New Operator 


Mode 


Obtained 


Stack 


Stack 


LI 


+4. 


4 


= 


L2 


t 


4 


=,t 


LI 


VAR 


4,VAR 


=,t 


LI 


(unstack) 


4tVAR 


= 


L2 


CR 


4tVAR 




Equation: X = 


(+4* -VAR +COS(SIN(- 


-Y))) (CR) 




Present 


Character 


New Operand 


New Operator 


Mode 


Obtained 


Stack 


Stack 


LI 


( 




=,( 


LI 


+4 


+4 


=,( 


L2 


* 


44 


= ,(,* 


LI 


-VAR 


4,0,VAR 


= ,(,*,- 


LI 


(unstack) 


(4*-VAR) 


-,( 


L2 


+ 


( ) 


=,(,+ 


LI 


COS( 


( ),COS 


=,(,+,$ 


LI 


SIN( 


( ),COS,SIN 


= ,(,+,$,$ 


LI 


-Y 


( ),COS,SIN,0,Y 


= ,(,+,$,$,- 


LI 


(unstack) 


( ),COS,SIN,(-Y) 


= ,(,+,$,$ 


L2 


) 


( ),COS,SIN(-Y) 


=,(,+,$ 


LI 


(unstack) 


(no change) 




L2 


) 


( ),COS,(SlN(-Y) 


= ,(,+ 


LI 


(unstack) 


( ) 


=,( 


L2 


) 


( ) 


= 


LI 


(unstack) 


no change 




L2 


CR 


exit 





Listing 3: Two examples of parsing done by ttie EVAL routine. The first equation is performed 
sequentially from left to right since there are no parentheses to change the order of execution. 
The second expression contains parentheses to modify the order of execution. The first opera- 
tion performed is the sine of — Y. The cosine of that value is then determined. The value of 
VA R is then subtracted from that value and added to +4. The symbol t /5 used to designate 
exponentiation. 



to evaluate the right side of the equation, 
then the value returned on the operand stack 
is transferred to the location assigned the 
variable. The FINSTM routine skips over any 
comment field up to the carriage return. 

EVAL: The EVAL routine uses a slightly 
modified Bauer-Samelson algorithm to deter- 
mine the order of execution of an expres- 
sion. [For a thorough discussion of this 
method see February 1976 BYTE, page 26. J 
The execution starts in the innermost 
parentheses and works from left to right 
without any consideration for precedence. 
Since many different types of precedence 
have been used in other languages, confusion 
is likely. This procedure minimizes the size 
of the stack and conforms with the conven- 
tions of APL and most assemblers. Prece- 
dence is established by parentheses which 
make the ordering unambiguous. 

The algorithm is shown in table 3 as an 
action table with two modes LI and L2. The 
algorithm starts in the LI mode, expecting 
an operand, which is a variable or a name. If 
an operand is found, the algorithm goes to 



the L2 mode, expecting an operator. After 
an operand is found, any operators at the 
top of the operation stack are executed. A 
flowchart of the algorithm is shown in figure 
2. 

Two examples of parsing by EVAL are 
shown in listing 3. The t symbol is used for 
exponentiation. In mode LI, the -•- and — are 
considered unary operators, but if they are 
encountered in mode L2 they are considered 
binary operators. This distinction is the 
rationale for operating in the two modes. 
The errors described in the table of figure 2 
cause the interpreter to terminate execution, 
print the line of code up to the error, and 
print an error message indicating the 
difficulty. 

IF: The routine shown in figure 3 first 
compares the variable with the expression 
and then the interpreter executes the code 
up to the corresponding ENDIF statement, 
but only if the variable meets the conditions 
specified by the IF statement. This routine 
uses the EVAL and SEARCH routines. 

A flowchart of the SEARCH routine is 



( '' ) 










GET 

VARIABLE 
AND ITS 
VALUE 










SET 

INEQUALITY 

FLAG 










CALL EVAL 




EVALUATE 
EXPRESSION 


/equality\y 
ssatisfied >■ 

NO 


ES 








CALL SEARCH 




LOOK FOR 
END, ENDIF, 
OR IF 


1 












CALL FINSTM 




SKIP THE 
COMMENT 
FIELD 








/^ GO TO A 
^^ SCAN J 





Figure 3: The IF routine 
evaluates the expression 
and then checks to see if 
the inequality has been 
satisfied. If the inequality 
is not satisfied it will per- 
form the operations 
between the IF statement 
and the line containing the 
ENDIF statement If the 
inequality is satisfied then 
the interpreter skips over 
the instructions and goes 
to the line of code directly 
after the ENDIF state- 
ment. 



luPy 1978IDBYTE Publications Inc 157 



shown in figure 4. The SEARCH routine 
scans the line of code trying to find an 
ENDIF statement. If another IF statement is 
encountered the subroutine calls itself to try 
to first find another ENDIF before it goes 
back to searching for the first ENDIF. If one 
ENDIF statement is not found for each IF 
before an END or ENDDO statement, an 
error is announced. 

An IF and its corresponding ENDIF may 
not straddle an ENDDO. If this were al- 
lowed, the data stored on the stack by the 
DO loop might not be unstacked as the DO 
loop is exited. 

Search: Each line of code is inspected 
until an END, ENDIF or IF is encountered. 
An IF causes the search to initiate another 
search for an ENDIF, an END causes an 
error, and an ENDIF causes a return. 



Figure 4: The SEA RCH routine inspects eacli line of code until an END, 
ENDIF or IF command is encountered. An I F statement causes the search to 
initiate another search for an ENDIF. Note that this means that the routine 
will be calling itself recursively, so care must be taken in allocating and pre- 
serving local data within SEARCH during recursion. An END statement 
causes an error and an ENDIF statement causes a return from the SEARCH 
routine. 



( SEARCH ) 



I IS 

I EXPRESSION 
END, ENDIF, 













GET NEXT 
EXPRESSION 




<-^ TE 


ST^\. 


MO 



ENDDO OR IF 



! '® 
EXPRESSION 

I 



TEST 



CALL SEARCH 



RECURSIVE 
SEARCH 



[IS I 

[EXPRESSION j_ 
(END OR ENDDO 
1. J 



TEST 


\YES 


OUTPUT 


-^ ? ^ 


y 


ERROR 


1 


NO 

















( RETURN j 



Figure 5: The DO routine will perform the operations between the line of 
code containing the DO statement and the line of code containing the 
ENDDO statement until the inequality is satisfied. When the inequality is 
satisfied the interpreter will exit the DO loop and perform the first line of 
code that follows the ENDDO statement. *- 





( - ) 










PUSH LINE 
POINTER 
ONTO 
STACK 












CALL FINSTM 






JUMP OVER 

COMMENT 

FIELD 














CALL SCAN 






EXECUTE 
INSTRUCTION 












PULL OLD 
LINE 
POINTER 
FROM STACK 














STORE LINE 
POINTER 
IN LINE 
POINTER 
REGISTER 














CALL FINSTM 






JUMP OVER 

COMMENT 

FIELD 














CALL SCAN 






EXECUTE 
INSTRUCTION 
















GET VARIABLE 
NAME VALUE 


1 UNTIL 
^INSTRUCTION_| 




1 






SET 

INEQUALITY 

FLAG 














CALL EVAL 






EVALUATE 
EQUATION 












DETERMINE 
VALUE OF 
INEQUALITY 




NO 


^Tn-^^ 

/equalit'n.y e s 
















PULL LINE 
POINTER 
OFF STACK 


















riNCREMENT "] 
' LINE POINTER ' 
1 TO FIRST 1 


SEARCH 

FOR 

ENDDO 




1 LINE AFTER | 
|_ENDDO J 

VES 








1" 




\^/ 




LINE 

POINTER. 

ENDDO+I 


NO 




1 




j^ ^\ 


10 


J 


\ "V y^ 




1 




Nc^ 




JUMP OVER 

COMMENT 

FIELD 




1 








OUTPUT 

ERROR 

MESSAGE 














1 






V scan" J 


( RETURN ) 



158 luly 1978©8YTE Publications Inc 



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Circle 74 on inquiry card. 



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Kit $98.00 

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Star Route, Box 241 

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Circle 377 on inquiry card. 



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Circle 77 on inquiry card. 



Circle 153 on inquiry card. 



Circle 223 on inquiry card. 



START OF 

RETURN 

ROUTINE 



CED 



f END j 



GET 

SUBROUTINE 

NAME 



FIND 

SUBROUTINE 
LOCATION IN 
LOOKUP 
TABLE 



GET 

VARIABLE 

VALUE 



/end ^ 

V ERROR y 



JUMP OVER 

COMMENT 

FIELD 



GET 

VARIABLE 

VALUE 



PUSH CURRENT 
LINE NUMBER 
ONTO STACK 



LINE 

POINTER:- 
SUBROUTINE 
LINE NUMBER 



RESET 

LINE 
POINTER 



OUTPUT 

ERROR 

MESSAGE 



EXECUTE 
INSTRUCTIONS 



CLEAR SYMBOL 
TABLE AND 
STACKS 



JUMP OVER 

COMMENT 

FIELD 



SKIP OVER 

COMMENT 

FIELD 



(GO TO \ 
MONITOR^ 



PULL OLD 
LINE POINTER 
OFF STACK 



f GO TO ^ 
V MONITORy 



JUMP OVER 

COMMENT 

FIELD 



EXECUTE 

INSTRUCTION 



Figure 7: The END statement should be the 
very last statement at the end of a program 
or subroutine. If during normal operation an 
END statement is encountered, there has 
been an error in execution. This END 
ERROR routine is used before the inter- 
preter exits to the monitor program. 



d 




PULL LOOP 

ADDRESS OFF 
STACK 



-*r 



SCAN NEXT 
LINE OF 
CODE 




OUTPUT 

ERROR 

MESSAGE 



TURN J 



Figure 6: Flowchart for the CALL and RETURN routines. The interpreter 
allows multiple return statements and allows the subroutine to have a return 
from within a DO loop. Subroutines may be nested with the only limit being 
the amount of memory space that is available for use by the stack. 



Figure 8: The EXIT routine transfers control 
back to the monitor program. The line 
pointer is reset to the beginning of the 
program, the stacks are reset to their original 
values, and the symbol table is cleared. 



DO: The flowchart of the DO routine is 
shown in figure 5. The DO loop routine 
stores the line pointer on the stack. The line 
pointer will be used later by the ENDDO 
macroinstruction to determine where to 
return in the source code. The use of a stack 
allows nested DO loops. The lack of state- 
ment labels excludes the possibility of errors 
caused by not nesting DO loops within each 
other (which is possible in a language like 
FORTRAN). 

The UNTIL instruction provides the 
means of exit from a DO loop. When the 
variable satisfies the inequality, the program 
moves to the code past the next ENDDO 
statement. For a DO loop of fixed length the 
variable must be initialized prior to the DO 
statement and incremented within the loop. 

Subroutine Call: The CALL routine 
shown in figure 6 determines the location of 
the subroutine code in the code list by 
looking up the location in a table. The table 
of locations is built for later use during the 
initialization process before any code is 
executed. The location of the current posi- 
tion in the code is saved in the stack. Usually 
the operand stack is used. 

The RETURN routine recovers from the 
subroutine by loading the old line address 
from the stack into the line pointer. A 
RETURN from within a DO loop presents a 
special problem which is resolved by search- 
ing for any lone ENDDO statements and 
pulling the loop address off of the stack. 

END and EXIT: The END routine is 
shown in figure 7. The END routine denotes 
the end of the program or subroutine. Its 
main purpose is to prevent the program 
execution from proceeding into another 
routine, causing an error. 

The EXIT routine shown in figure 8 is 
responsible for transferring control back to 
the monitor and mopping up chores such as 
resetting the line pointer to the beginning, 
resetting stacks, and clearing the symbol 
table. It normally would not clear the 
subroutine table as the code may be rerun 
later. 

Conclusion 

The interpreter is especially adapted to 
interactive programming. The language 



160 



|ulv 1978©BYTt Publkalions liic 



Circle 190 on inquiry card. 



presented here is tailored to structured 
programming techniques which can yield 
clear, precise code. Our implementation of 
the interpreter is written in a macrolanguage 
which may be adapted to any microproces- 
sor by defining each macroinstruction in the 
assembly language of the microprocessor. A 
compiler for the same macrolanguage was 
also written so that a resident machine 
language version may be made when it is 
required. 

The main features of this interpreter are: 
the structured language, the methods for 
evaluating expressions, and the methods for 
handling lO. Much of the detail in handling 
data is taken over by the interpreter so that 
only the fundamental considerations must 
be considered in writing a program." 

BIBLIOGRAPHY 

1. Bloom, A IVI, "The ELSE must go to," Data- 
mation, pages 123 to 128, IVlay 1975. 

2. Maurer, W D, "Processing Algebraic Expres- 
sions," BYTE, pages 26 to 30, February 1976. 

3. Kerninghan and Plauger, The Elements of 
Programming Style, McGraw Hill, New York, 
1974. 



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Circle 84 on inquiry card. 



July 1978 © BYTE Publications Inc 161 



How To Get 



Larry Weinstein 
Objective Design Inc 
POB 20325 
Tallahassee FL 32304 



Your Tarbell Going 



General Theory 

The function of the Tarbell cassette 
interface (referred to as the "Tarbell") 
is to enable a computer system to save the 
contents of memory on audio tape. The pur- 
pose of this article is to explain how the 
Tarbell interface works and to suggest some 
improvements to its design for readers who 
have had difficulties with the unit. 

The Tarbell is intended for use with 
inexpensive cassette recorders: the inputs 
and outputs are matched for the typical 
Aux In, Ext Spkr and Earphone connec- 
tions. The computer interface to the Tarbell 
is on a byte level, with the bytes and com- 
mands passed by 10 instructions on the 
Altair (S-100) bus. 



ANALOG SECTION 



CASSETTE 




Figure 7 : Block diagram oftfie Tarbeli cassette interface board. 



The Tarbell converts digital information 
to an audio form that can be written on 
magnetic tape. In turn, it recovers the 
digital data from the audio signal. These 
are the primary functions; the rest have to 
do with the "housekeeping" involved with 
the Altair (S-100) interface. 

Figure 1 shows a simplified block draw- 
ing of the Tarbell. 

A cassette recorder has definite fre- 
quency limitations. The higher the fre- 
quency, the less accurate the signal repro- 
duction will be. On the other hand, speed 
of operation is critical for the success of a 
storage medium. The Tarbell makes its 
compromise at approximately 1500 bps. 
This is determined by the interface clock. 

The rate of data flow to the cassette 
must be known if the data is to be re- 
covered. At first it might seem that we 
could use the same clock to move raw data 
to and from the tape. The problem is that a 
cumulative error will quickly build up when 
a long stream of data is read. There are two 
solutions to this. First, write the data only 
in small groups (say ten bits) with definite 
start and stop points in each group. This 
is called asynchronous recording. Second, 
write long uninterrupted data streams and 
include some clock information with the 
data. This is called synchronous recording. 

The Tarbell generates synchronous data 
streams. Some clock information is added 
to the data by a technique known as phase 
encoding. To phase encode, one simply 
performs an exclusive OR operation with the 
clock and data (see figure 2). The Tarbell 
block diagram now takes on the form of 
figure 3. 



162 )ulv 1978 e BYTE Publications Inc 



Note that phase encoding does not mean 
that the decoding circuitry is free from the 
tasl< of generating a matching clocl<. This 
will still be a critical part of the operation. 
We have simply eliminated the possibility 
o^ cumulative timing errors. 

Assembly 

The Tarbell cassette interface board is 
plated through but does not use a solder 
mask or silk screen printing. A 30 page 
manual is included with all needed parts. 
The kit does not include sockets for inte- 
grated circuits. 

Assembly is not difficult. The original 
design lacked several pull up resistors and 
small capacitors, which led to noise prob- 
lems. Subsequent revisions have incor- 
porated these parts without any major 
board changes. Consequently, some of these 
parts are in unlikely places. A careful ex- 
amination of the assembly drawing is re- 
quired. If you have access to a copying 
machine, I suggest that you copy the parts 
list, assembly drawing, and two schematic 
pages to facilitate construction. Repeatedly 
flipping back and forth in the manual be- 
comes tiring and one does not feel so bad 
about checking off items in pencil on a 
working copy as construction progresses. 

There is a 50 k potentiometer on the 
board that is inappropriate. It is of the 
thumbwheel variety, and is too big: you 
cannot insert a board in the Altair bus slot 
directly in front of a Tarbell. There are also 
electronic problems with this part, which we 
will get to presently. 

Operation (Digital Sections) 

For output, bytes are loaded into a shift 
register. A timer clocks data out of the 
register into an exclusive OR gate. The same 
timing signal goes into the other input of 
the exclusive OR. The result is that a phase 
encoded signal is written onto the tape. A 
status bit informs the computer program 
that the last bit is being transmitted and the 
next byte can be loaded. 

For input, the decoded clock signal feeds 
the data into a shift register. For startup, the 
register is examined for a sync byte. When 
this pattern is detected, a modulo 8 counter 



CLOCK 































1 


DATA 


























PHASE 


































ENCODED 
RESULT 



Figure 2: Phase encoding. Tine Tarbell interface uses this technique, which 
involves performing an exclusive OR operation with the clock and the data. 



is enabled. This counter flags the computer 
program after eight new bits (byte) are 
loaded into the shift register. The sync 
byte pattern (hexadecimal E6, or binary 
11100110) is hardwired into the interface. 
A cassette with a sync stream written on 
it is supplied. An LED on the Tarbell is 
supposed to light up when the aforemen- 
tioned sync code is detected. The setup 
operation consists of adjusting the cassette 
volume control and the 50 k pot until the 
LED remains on with a steady light. Here is 
where the difficulties begin. 



CLOCK 



SHIFT OUT 




ANALOG SECTION 



ENCODE 




-o 



SHIFT IN 



BUS 
INTERFACE 



?^ 



^Z 




DATA 



-<:] 



CASSETTE 



BUS 
INTERFACE 



Figure 3: A more de- 
tailed block diagram of 
the Tarbell cassette inter- 
face showing the phase 
encoding and decoding 
procedures. 



luly 1978 © BYTE Publications Inc 163 



74L86 



CLOCK 
DATA 



M 

\ IKA 




IIKii 



@ OUTPUT TO CASSETTE 
AUX INPUT 



r.luF 



/77 ft? rh 



J~U 



Figure 4: Output section of the Tarbell interface. Tlie circuit contains a 
simple low pass filter with a cutoff frequency of 1.5 kHz. The filter eliminates 
the high order harmonics to produce an approximate sine wave, which is 
then recorded onto the cassette. 



The presence of a steady sync light is a 
good indication, but it does not guarantee 
the ability to read long files. A single missed 
clock pulse in the sync stream will almost 
certainly go unnoticed. However, a single 
missed clock pulse during the reading of a 
data file will cause the subsequent bits to 
be read incorrectly. Also, the sync stream 
does not have a 010 pattern in it, which 
turns out to be a prime candidate for drop- 
ping a clock pulse. 

With some cassette players and Tarbell 
combinations, the control settings are non- 
critical. The lack of a good setup indicator 
isn't important in these cases. On other 
cassette players the settings are critical; 
extremely so. Here, the absence of a source 
of feedback for the setup is sorely missed. 

Our early experiences with the Tarbell 
were problematical. As we began to look 



RECOVERED 
DATA 




CASSETTE C6 
INPUT .02 



*0N SOME MODELS, THIS MAY BE A 2.4K RESISTOR 



Figure 5: Input circuitry of the Tarbell cassette interface (internal details of the 8T20 circuit have been included for clarity). 
The incoming sine wave signal is transformed into a digital signal by the comparator circuit inside the 8T20 (see figure 6). 



1 64 July 1978 e BYTE Publications Inc 



more closely at the device, we ran into more 
questions than answers. For example: 

A. Why do different Tarbell units have 
different levels of reliability? 

B. Why do seemingly equivalent tape 
decks yield different performances? 

C. Why will a very cheap cassette machine 
outperform one costing many times 
more money? 

D. Why do some very good cassette tape 
brands fail to do well with the Tarbell, 
while others, even less expensive 
ones, do a fine job? 

E. Why must (as the manual recommends) 
the tone control be placed at maxi- 
mum treble? With the highest fre- 
quency we wish to have on the tape 
being 1500 Hz, the results should be 
better with the tone control on a 
high bass setting. 

F. How were the resistance and capaci- 
tance values in the analog sections 
chosen? 

With these questions in mind, we took a 
closer look at the Tarbell and came up with 
the following information. 

The critical part of any tape storage sys- 
tem is the analog input section. The entire 
digital data and clock recovery circuit of 
the Tarbell is constructed from a single 
IC (the 8T20) and a few passive components. 

Figure 4 gives the output section. This is 
really a simple low pass filter with a cutoff 
frequency of 1.5 kHz. The filter eliminates 
the high order harmonics of the output digi- 
tal signal. The result is a sine wave, or nearly 
so. 

The input section of the Tarbell is shown 
in figure 5. We have drawn out the internal 
8T20 circuitry. Data on the 8T20 in the 
early Tarbell manuals was absent. 

To recover the data, it is first necessary 
to convert the sine wave recovered from the 
cassette unit to a digital signal. Assume for 
the moment that the sine wave is symmetric 
about V. A comparator with one input 
grounded (a zero detect circuit) would then 
produce a digital signal that matches the 
original one (see figure 6). 

Once the input signal passes through C6 
(a 0.2 juF capacitor in the Tarbell input sec- 
tion), it loses any DC level. The DC level is 
then set by the 9 k and 5 k voltage divider 
resistors inside the 8T20. To convert the 
signal properly, the positive input of the 
8T20 comparator must also be set to this 
voltage. This is accomplished by the voltage 
divider formed by Rl and R3. As figure 5 
shows, R2 and diode CRT play a part in 



this circuit by providing hysteresis: When 
the output of the comparator is high the 
divider circuit is electrically equivalent to 
figure 7a. When the output is low, the cir- 
cuit is roughly equal to that of figure 7b. 
The effect of this is to eliminate oscillation 
about the bias point. 




1 I I I I ■ > 'I 

LnLr~L_rL_rL b 



m 



Figure 6: Action of ttie comparator inside the 8T20 circuit. T/ie comparator 
acts as a zero crossover detector to transform the sinusoidal input from the 
cassette into a stream of digital pulses. 



(7a) 



(7b) 



+ 5 



+5 



: 3K 



H > 1.9V i lO-i 



3K 



-| > 1.6V ±10% 



; I.5K 



|l.5K I 4.7K 



rn 



m ftt 




Figure 7: Equivalent circuits for the voltage divider input circuit (Rl, R3, 
R2 and Dl) in figure 5, plus the resulting output waveform. Figure 7a shows 
the equivalent circuit for the case when the comparator is high, and figure 7b 
shows the equivalent circuit when the comparator is low. Figure 7c is the 
output waveform. This hysteresis effect is designed to eliminate oscillation 
of the comparator if a signal "hovers" about the bias point. 



July 1978 e BYTE Publications Inc 16S 



~L_^ 



ORIGINAL DATA 



~L 



J \ r 



ORIGINAL 
CLOCK 



M0N0STA8LE 
TRIGGER 




ENCODED 
SIGNAL 



RECOVERED 
CLOCK 



^ PULSE IS 75% OF CLOCK PERIOD, T^ 



Figure 8: Recovery of the clock from the 
encoded signal. The encoded signal Is formed 
by performing an exclusive OR operation on 
the data and the clock. To recover the clock, 
a one shot with a duration of exactly 0. 75 
clock cycles fires on every transition of the 
encoded signal. 



RESULT OF ALL Is 
OR ALL Os 

\ 

~L_r~L_r 



I TO OR TO I 

TRANSITION IN ORIGINAL DATA 



J~~LJ L_r^ 



_l U U \ \ U U U LT 



\ 



CLOCK RECOVERY 
OUT OF SYNC 



NOW IN SYNC 



Figure 9: Automatic synchronization of the 
one shot (monostable) pulses and the signal 
transitions (see figure 8). As soon as a I to 
or a to I transition takes place In the 
data, the recovery one shot is forced to 
"fall in line." 



Figure JO: Complete timing diagram for signal processing In the Tarbell 
interface. 



HEXADECIMAL 22 



E6H-SYNC BYTE 



OOIOOOIOI I 1001 10 











— 








— 




A 


A 


r 






f\ 


/ 




— 


A i 


r\ 


r\ 


— 


\ 


^ 


— 


^, 


\ 


f\ 


- 
\ 


^. 


/ 


f\^ 


(*'i. 


\j 


\J 


1 — 


1 — 

H 


y 


\J 


\J 


V 


y 


V 


y 


J^ 


J 


\J 


V 


J 


J 


\J 




- 


— 




' — 


































































— 





















ORIGINAL DATA TO TARBELL 



ORIGINAL CLOCK 



PHASE ENCODED CLOCK AND DATA 



ANALOG SIGNAL TO AND FROM 

CASSETTE 

ASSUMES "PERFECT" REPRODUCTION 



DIGITAL SIGNAL RECOVERED FROM 
ANALOG 



RECOVERED CLOCK - GENERATED BY 
MONOSTABLE 



RECOVERED DATA-WHICH IS INVERTED 



INVERT TO ORIGINAL DATA 



DATA BECOMES VALID AFTER FIRST 
TO I TRANSITION 



®THIS LOW FREQUENCY WAVE WILL OFTEN BE LOW IN 
VOLUME AND DISTORTED, RESULTING IN A DROPPED 
CLOCK AND LOSS OF SYNCHRON IZ ATION 



166 lulv 197S ' BYTE Publicalion* In 




SYMMETRIC SINE WAVE 
INPUT TO COMPARATOR 



DC "TRIGGER" LEVELS, 
WITH HYSTERESIS, 
INPUT TO COMPARATOR 
SHOWN INCORRECTLY 
SET FOR SINE WAVE, 
TRUE DC LEVEL 



SINE WAVE DC LEVEL 



SYMMETRIC RESULT OF 
MATCHED DC LEVELS INPUTS TO 
COMPARATOR 



ASYMMETRIC RESULT OF 
MISMATCHED DC LEVELS, WITH 
HYSTERESIS 



Figure 1 1 : Effect of mis- 
matched comparator input 
DC levels. 



CI 6 reduces any very high frequency 
noise coming in on the line. C6, besides 
serving as a coupling capacitor, also forms 
a filter with the 8T20's internal 5 k resistor. 
The effect is to reduce the low frequency 
part of the signal. It is also an effective 
60 Hz and "wow" filter. 

Once the original digital signal has been 
recovered, we can proceed to reconstruct the 
clock signal, and from that, the data. On 
every transition of the digital signal, a 
monostable is triggered (see figure 8). The 
timing of the pulse is critical. It should be 
75% of the period of the output clock. 
(You may have to study figure 8 carefully 
in order to understand how this recovery 
process works.) 

Next, examine figure 9. It shows the 
automatic synchronization process of the 
monostable pulses and the signal transi- 
tions. As soon as a 1 to or a to 1 transi- 
tion occurs in the original data, the recovery 
monostable is forced to "fall in line." For 
this reason, some kind of start byte is re- 
quired ahead of the normal sync byte when 
using the Tarbell. The entire process is 
shown in figure 10. 

The major problem with this circuit is 
its sensitivity to waveshape and amplitude. 
The primary cause of this rests in the way 
the DC levels are set for the comparator. 
The 8T20 specifications give the reference 
voltage available at pin 7 as a nominal 1 .4 V, 
with minimum and maximum values of 0.8 



and 2.0 V, respectively. Since the "+" input 
to the comparator is set by an independent 
voltage divider, an error of half a volt is 
possible. Figure 11 shows the effect of mis- 
matched DC levels. As you can see, the 
more closely these DC levels are matched, 
the better off you will be. 

The timing distortion produced by this 
effect can be compensated for by the proper 
setting of the monostable, up to a point. 
However, the more the timing is off, the 
more critical the pot setting will be. 

The monostable pulse time is determined 
by C7 and R8, a 50 k pot. The timing is 
defined by the relation: 

Tw=(C)(R)(ln2) 

For the given Tarbell output frequency we 
require a pulse of (.67 ms) (0.75) = 0.5 ms. 
Therefore, the R/C relation is R= .72/C,with 
R in kilohms and C in microfarads. For a 
.033 mF capacitor, R should be 21.85 kf2; 
for .039 ixV, it should be 18.5 kfi. A large 
fixed resistor in series with a 5 ki2 trimpot 
would do a far better job here. 

The next factor affecting this timing is 
in the cassette transport itself. Flutter, a 
high frequency variation in tape speed, will 
cause the sine waves to vary in period. 
Figure 1 2a shows the effect of flutter. 

The shape, symmetry, and amplitude 
of the wave will also affect this timing. 
Inexpensive tape machines generally use 
tone controls that work in tandem with the 



|uly 1978 ' BVT[ Publications Inc 167 



02a) 



(12b) 



(12c) 






(12d) 



(12e) 





J" 



1 



Figure 12: Factors causing timing distortion in Tarbell processed signals. Figure 12a shows tfie 
effects of flutter, orhigfi frequency variations in tape speed. Figures 12a, 12b and 12c illustrate 
the effects of shape, symmetry and amplitude, respectively, of the signal waveform on the 
digitized output. Figure 1 2 shows how changes in signal amplitude caused by the low pass filter 
in the input circuit (see C6 in figure 5) can affect pulse width. 




HYSTERESIS PRESENT 



Figure 13: Effect of the presence of hys- 
teresis: a sudden unexplained dip in DC 
level. 




Figure 14: High amplitude signal with steep 
sides resulting from a high treble setting on 
the cassette recorder. 



volume control. Each will affect the other. 
The effects of these factors are shown in 
figures 12b, c, and d. 

The high pass filter created by C6 in the 
Tarbell causes the amplitude of the input 
signal to vary according to frequency. The 
result is shown in figure 1 2e. This frequency 
change area is already a sensitive point; 
the mismatch of amplitudes compounds 
matters. 

We noticed one additional effect in a 
Tarbell unit, for which we have no explana- 
tion as yet. The input appears as in figure 1 3 
whenever the hysteresis circuit is connected. 
With the hysteresis removed the wave 
oscillates about a fixed center line. 

Bearing all of this in mind, we're ready 
to try for some answers. 

Tarbell units with the more closely 
matched DC level inputs to their comparators 
will be less sensitive to all of the factors 
that can cause problems. A very slight 
difference, even 200 mV, is significant. 

Also, the higher the input signal ampli- 



168 July 1978 e BYTE Publicitiominc 



tude, the less likely any of the waveshape 
factors are to have any effect. 

Why do some Tarbell units work in the 
higher end of their volume range but not at 
the very top? This is due to the connection 
between the volume and tone controls. 
When the volume is at maximum, especially 
where the treble control is also at an ex- 
treme, the waveshape is severely distorted. 

When the tone control is at maximum, 
the amplitude of the signal is increased and 
the waveshape is affected. The general out- 
come is a wave with steep sides about the 
"zero level" (see figure 14). The amplitude 
increase and steep sides tend to produce a 
more accurate digital signal. 

A high bass setting reduces the amplitude 
of the wave with a greater effect on the 
higher frequency section. With some cassette 
players, a full bass setting can produce up 
to a 3 dB per octave loss beginning in the 
area of a few hundred Hz. It is the overall 
signal loss that makes a high bass tone setting 
unacceptable. 



Figure 15: Suggested changes to the Tarbell 
front end circuitry. 



CASSETTE 
INPUT 



(OR USE LOGIC 
PROBE HERE) 



o 



REMOVING 
RESISTOR 
MAY IMPROVE 
PERFORMANCE 



5 OR 10 K 
POT 
y^ 




1 



I.5K 



-REMOVE HYSTERESIS 



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AAAIN OFFICE: 121 EAST ELEVENTH AVE. • EUGENE, OREGON 97401 • (503) 485-0626 



Circle 287 on inquiry card. 



July 1978 ©BYTE Publications Inc 169 



Listing 1: The author's 
test tape for the Tarbell 
cassette interface. 



The presence of even mild dropouts on 
the cassette tape will also cause problems. 
A 1 ms loss of a few decibels of output level 
wouldn't be noticed in audio work, but 
could mean the fatal dropping of a clock 
pulse when recording digital information. 
Thus, some cassette tapes that pass audio 
tests with flying colors may be unacceptable 
for digital applications. (We have had ex- 
cellent results with Scotch low noise, high 
density C-60 tape.) 

As for the differences in cassette decks, 
there are many possible factors: probably 
the main one is the amplitude of the output 
signal. However, the amplitude effect is 
closely tied to the waveshape, and a pure 
sinewave does not always yield the best 
results. In other words, high cost and ac- 
curate reproduction do not guarantee good 
performance. 



eeea 








CASC 




tl'' 


6E.1 






00^0 








CASE 




E21I 


6FH 






0200 








* 












BCeB 






- 


* '..'T'lTl 


OUT 


STHtAM OF ALTEP.NATING 


ez0P 








» SYNC (E6H) EYTE 


-S ANt; TEST 


C22H) BYTES 


e e?0 








* 












01300 


06 


22 




LOOPV 




MVI 


b.. 2 2K 






0002 


CD 


0D 


00 






CALL 


fi'b 






000? 


06 


E6 








MVI 


E/L''16H 






0007 


CD 


0D 


00 






CALL 


SUB 






0e0A 


C3 


00 


00 






JMP 


LOOPU 






000D 








« 












000D 








• SI'B VI 


LL 


VPITE 


TO THE TAPbELL ■ • 


000D 








+ 












000D 


DB 


6E 




SUB 




IN 


CASC 


» 


TEST STATUS 


0eF 


E6 


20 








AN I 


2 0H 






001 1 


C2 


0D 


00 






jn: 


SUB 






001-1 


78 










MOV 


A..b 






001 E 


D3 


6E 








OUT 


CASC 


* 


OUTPUT BYTE 


0017 


C9 










RET 








0013 








* 












0018 








♦ TEST PROG 


PAM = 


THE TAPE GENEFATED 


eeis 








* ABOVE 


IS 


PLAY EI 


) ".EULE PUNNING THIS 


0018 








* PPOGP.AM. 


A SIGNAL CBELLj 


BEEP. OR 


0018 








* LIGHT) 


IMPLI ES 


AN ERROR DETECTED. 


e 018 








* 












0018 


3E 


10 




TEST 




MVI 


A- 10H 






001A 


D3 


6E 








OUT 


CASC 


« 


RESET TARBELL 


01C 








« 












0010 


06 


22 




LOOPR 




MVI 


B/22H 






001E 


CD 


32 


00 






CALL 


SUBP. 


« 


READ BYTE 


0021 


C2 


EC 


00 






JNZ 


MISS 


* 


NZ--NOT 22H. ERR 


024 


06 


E6 








MVI 


b>0E6H 


* 


22H. CHECK SYNC 


026 


CD 


32 


00 






CALL 


SUBR 






0029 


CA 


IC 


00 






JZ 


LOOPR 


* 


SYNC OK- LOOP 


02C 








* 












002C 








* EEH MISSED- GIVE ERPOB SIGNAL. 


002C 


CD 


3C 


00 


HISS 




CALL 


SIG 


* 


USER SUPPLIED 


e02F 








« 












002F 


C3 


18 


00 






JMP 


TEST 


* 


RESET- RESTART 


0032 








* 












0032 


DB 


6E 




SUBP. 




IN 


CASC 






0034 


E6 


10 








AMI 


IZH 


« 


BYTE READY? 


036 


C2 


32 


00 






JNZ 


SUBR 






0039 


DB 


6E 








IN 


CASD 


* 


INPUT BYTE 


003B 


B8 










CMP 


B 


« 


COMPARE 


003C 


C9 










RET 








003D 








* 












03D 








SIG 




DS 


20D 


^ 


ADD SIGNAL HERE. 


0051 








* 












PEADY 


















CASC 


006E 


CASD 


006F LOOP. 


' 0000 


SUB 000D 






TEST 


0018 


LOOPP. 


001C MISS 


002C 


SUBR 0032 






SIG 


003D 

















Corrections 

A few simple changes in the Tarbell input 
section will significantly improve perform- 
ance. (Refer to figure 15.) 

First, remove the hysteresis circuit, 
either by cutting the trace on the rear of 
the card that connects R2 to CRT, or by 
simply removing one of these two com- 
ponents. If you are a diehard believer in 
hysteresis, replace R2 with a 47 k or larger 
resistor. Bear in mind that the 8T20 specs 
give a ±4 mV input threshold. 

Next, replace R1 with a 5 k or 10 k pot. 
This will enable you to set the "-i-" input 
level to match the signal DC level. 

Set up the Tarbell with its cassette 
player. Place a logic probe on pin 1 or 9 of 
the 8T20 (or add a resistor and LED as in 
figure 15). With the cassette player off, 
adjust the R1 replacement pot near the 
area where the light switches from on to 
off. 

Set the tone and volume controls to their 
halfway points. Use the program in listing 1 
to generate a test tape. Note that a special 
test byte (hexadecimal 22, binary 00100010) 
alternates with sync. 

Now play back the tape with the test 
program running. A signal (light, beep, 
etc) implies an error. First adjust the 50 k 
Tarbell pot. You should be able to get a 
steady sync light with few or no error 
signals. From there, adjust the volume and 
tone controls until you can run a long test 
without a single error signal. As with a well 
running Tarbell, you should have a large 
range of acceptable cassette settings. 

Our experiences with Tarbells with these 
few changes have been excellent. They are 
totally reliable. Further, tapes written on 
other systems, can generally be read without 
readjusting the various control settings. 

Conclusions 

With revision D of the board, the noise 
prone floating inputs have been tied down 
(or up). But the input circuit i-j still lacking. 
The 8T20 internal bias resistors are clearly 
intended for use with a TTL input, not an 
analog one. The lack of adjustment on this 
bias will continue to cause problems, necessi- 
tating fixes such as the one given. 

On the plus side, the Tarbell is a con- 
tinually evolving and improving device. The 
responsiveness of its manufacturer (Don 
Tarbell) is unsurpassed in the industry. 



1 70 )uly 1978 © BYTE Publications Inc 



The board is available, has no "exotic" 
components, and is simple to set up and use. 
The cassette writing scheme which the 
Tarbell executes is one of several cassette 
methodologies now being used in the per- 
sonal computing field. Several versions of 
this type of recording method are now 
available in the hobby market. The 1500 bps 



speed is acceptable for work with small to 
medium length data files. For program load- 
ing, it is excellent. 

We'll take this opportunity to cast our 
vote for phase encoding at 800 bits per inch 
as a cassette standard and recommend it, 
from whatever manufacturer, for small 
computer systems." 



Manufacturer's Reply 

Thanks for the opportunity to reply to 
Larry Weinstein 's article. 

First, to reply to the questions posed: 
A, B, C, and D are somewhat, related. The 
main source of reliability problems we have 
found on the interface is faulty integrated 
circuits. These are sometimes difficult to 
isolate, especially when the problem is not 
occurring all the time. Tape drives vary 
considerably in their performance charac- 
teristics. The main requirements for our in- 
terface are a frequency response to 8000 Hz, 
and an output amplitude of at least 5 V 
peak to peak. We haven't found any recorders 
that have these characteristics that haven't 
worked with the interface. Some expensive 
recorders, sadly, don't have the above 
minimum requirements. 

As mentioned in question E, the highest 
frequency the interface works with is ap- 
parently 1 500 Hz. A certain number of har- 
monics above this, however, are required to 
accurately reproduce the phase shifts that 
this method uses. That's why it's usually 
better to have the tone set high. To answer 
question F, the parts values were generally 
first chosen by a combination of calculation 
and experience. They were then tuned 
empirically (ie: diddled on the breadboard) 
for optimum operation. 

I don 't think of C6 as a filter capacitor so 
much as I think of it as a differentiating 
capacitor. Its main purpose in my mind, 
in addition to removing the DC component, 
is to translate the peaks of the Input wave- 
form into zero crossings. In this way, the 
circuit becomes less dependent on input 
amplitude. Although the worst case toler- 
ances of the components in the input sec 
tion theoretically could cause a problem, 
our experience is that they don't. Out of the 



many units that have been returned for 
repair, none required adjustment or replace- 
ment of these components to make them 
work. On the other hand, it is true that 
replacement of Rl with a potentiometer 
could mean the difference between operating 
or not operating with a marginal recorder. 
The reason that a pot was not used in the 
design Is that I felt the fewer pots there were 
to adjust, the better off the user would be. 

We don't put a fixed resistor in series 
with the 50 k pot because we want to allow 
the user to adapt to much faster or slower 
speeds, as his requirement dictates. The 
reason for the hysteresis is to reduce the 
effects of noise on the input signal. With a 
sufficient amount of input amplitude, the 
percentage of distortion introduced by the 
hysteresis is minimal. IVIany computers have 
a fairly high level of noise, and so do many 
recorders. If you have a very clean system, 
you may not need the hysteresis, and can 
remove it as he suggests. This will also allow 
you to work with lower amplitudes, such 
as are generated by tape decks without 
amplifiers. 

In spite of the above comments, I feel 
that Mr Weinstein 's article is a valuable 
one, and is accurate, on the whole. His test 
program, especially, is excellent. I hope, 
however, that readers will not try the 
changes suggested in the article unless they 
actually are having problems. I would also 
like to take this opportunity to announce 
that the 90 day, no fault warranty on this 
product has now been extended to six 
months, and to encourage customers to send 
their boards back for a quick repair. 

Donald E Tarbell 

Tarbell Electronics 

20620 S Leapwood Av, Suite P 

Carson CA 90746 



luly 1978 (S BYTE Publicitions Inc 



171 



Now, a book 

for the practicing 

professional... 




"This is the best liandbook of data 
communications system technology 
that this reviewer has yet 
oicoiintered." — Arvid G. Larson in 
ACM Computin g Reviews 
February 19 78 

Digital Press announces the 
publication of TECHNICAL 
ASPECTS OF DATA COMMUNI- 
CATION by John McNamara. 

Written for the practicing pro- 
fessional, TECHNICAL ASPECTS 
OF DATA COMMUNICATION 
details the nuts-and-bolts prob- 
lems and solutions in configuring 
communications systems. It 
features: • comparison of protocols 
(DDCMP, BISYNC, SDLC) • exten- 
sive explanation of interface stand- 
ards (CCm/V.24, RS232C, RS422, 
RS423) • six comprehensive 
appendices (how far/how fast?, 
modem options, codes, UART, 
format and speed table for asyn- 
chronous communication, chan- 
nel conditioning) • 20 milliampere 
loop • telephone switching 
systems • error detection 

• 382 pages • 125 figures • 70 
pages of tables • index • hardcover 



mma 



Digital Press 
Educational Services 
Digital Equipment Corp. 
Crosby Drive, Bedford, MA 01730 

I would like to order copies of 

TECHNICAL ASPECTS OF DATA 

COMMUNICATION at $19.95 per copy, 

n Check enclosed D Money Order enclosed 

(Note: Minimum order for Digital Press to 

process purchase order is $35). 

Name 



Address- 
City 



_State_ 



_Zip_ 



Prices apply in U.S. only. B78 

172 (uly I9780BYTE Publications Inc 



Event Ousus 



This month we begin a formal Event 
Queue, a calendar of coming events 
which we t^now about as of press time. 
In order to gain optimum coverage of 
your organization's meetings, computer 
conferences, seminars, workshops, etc, 
notice should reach our office at least 
three months in advance of the date of 
the event. Entries should be sent to: 

Event Queue 
BYTE magazine 
70 Main St 
Peterborough NH 03458 

Each month we publish the current 
contents of the queue for the month of 
the cover date, and the two following 
calendar months. Thus a given event may 
appear as many as three times in this 
section if it Is sent to us far enough in 
advance. 



July 17-19, Data Processing Operations 
Management, Houston TX. This seminar 
will offer the senior data processing 
professional an opportunity to gather 
the latest management skills. The cur- 
riculum is designed toward practical, 
applied data processing management 
techniques. Contact Philip M Nowlen, 
Program Chairman, Director, Center 
for Continuing Education, University of 
Chicago, 1307 E 60th St, Chicago IL 
60637. 

July 17-21, Coding and Information 
Theory, UCLA, Los Angeles CA. This 
course will present the fundamentals of 
representation, storage and transmission 
of data. Protection against storage and 
transmission errors using error detection 
and error correcting (including ham- 
ming) codes will be developed. Effi- 
ciency enhancement through infor- 
mation compressing codes, predictive 
run encoding and Markov chains (pro- 
babilistic finite state machines) will be 
discussed. Contact Short Course Program 
Office, 6266 Boelter Hall, UCLA Exten- 
sion, Los Angeles CA 90024, (213) 
825-3344 or 825-1295. 

July 25-26, Workshop on Use of Com- 
puters in Teaching Statistics, University 
of New Hampshire, Durham NH. Work- 
shop participants will be scheduled for 
hands-on use of the following packages: 
Minitab II, IDA, SAS, SPSS and BMDP. 
Contact Dr Jerry Warren, Director, The 
Office of Academic Computing, 304 
McConnell Hall, University of New 
Hampshire, Durham NH 03824. 



July 26, Third Annual Indy Micro- 
computer Show, Holiday Inn, Indi- 
anapolis IN. There will be exhibits, 
demonstrations and technical seminars 
addressing the engineering, industrial, 
scientific, business and personal applica- 
tions of microcomputersystems. Contact 
Thurman H Gladden, Naval Avionics 
Center, D-810, 600 E 21st St, Indi- 
anapolis IN 46218,(317)353-3208. 

July 31 -August 4, Digital Filters, Uni- 
versity of Toronto CANADA. This 
course will provide a practical intro- 
duction to the subject of digital filters. 
Topics will include the frequency ap- 
proach, Fourier series and integrals, non- 
recursive filter design, theory of recursive 
filter design, discrete Fourier transforms, 
fast Fourier transform implementation, 
estimation of power spectra and non- 
linear phenomena due to quantizing 
signals. This course will be of interest to 
those who use linear combinations of 
data. The emphasis is on its basic nature 
and practicability. Contact Nonie 
Watanabe, Short Courses, 6266 Boelter 
Hall, UCLA Extension, Los Angeles CA 
90024. 

August 7-9, Third Jerusalem Conference 
on Information, Jerusalem ISRAEL. 
The conference will cover a broad range 
of topics on computing applications, 
science and technology. Primary empha- 
sis will be on the role of computers in 
the transfer of technology between large 
and small countries. Contact Robert W 
Rector, Executive Director, AFIPS, 210 
Summit Av, Montvale NJ 07645,(201) 
391-9810. 

August 7-9, Laser Beam Information 
Systems, Minneapolis MN. This sem- 
inar will cover the growing applica- 
tion of laser technology in image and 
data manipulation in the form of scan- 
ning, transmission, reproduction and 
control. The principles and practice of 
laser beam information systems will be 
covered in preparation for direct appli- 
cation to such fields as facsimile, com- 
puter memory and display, target 
identification, reconnaissance, photo- 
composition and image manipulation. 
Contact Philip M Nowlen, Program 
Chairman, Director, Center for Con- 
tinuing Education, the University of 
Chicago, 1307 E 60th St, Chicago IL 
60637. 

August 7-11, Coding and Informa- 
tion Theory, University of Toronto 
CANADA. See July 17-21, UCLA, 
for information. 



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Circle 250 on inquiry card. 



August 21-25, Digital Filters, UCLA. See 
July 31-August 4, University of Toronto, 
for information. 

August 21 -September 2, Courses on 
Microcomputer Interfacing and Ana- 
log Signal Conditioning, Virginia Poly- 
technic Institute and State University, 
Blacksburg VA 24060. The objective of 
these programs is to provide an educa- 
tional experience for scientists, engin- 
eers, teachers, managers or technicians in 
the areas of microcomputer data acquisi- 
tion, instrumentation, and measurement 
systems ranging from the analog sensor 
through the analog data channels to the 
microcomputer. The courses provide a 
combined lecture/ laboratory experience. 
Continuing education units are provided 
for each course. Contact Dr Linda 
Leffel, Center for Continuing Educa- 
tion, Virginia Polytechnic Institute and 
State University, Blacksburg VA 24061, 
(303) 951-5241. 

August 24-27, PC '78, Philadelphia 
Civic Center, Philadelphia PA. The 
first day of PC 78 (August 24) will 
be an industry trade show which is 
open to dealers, the industry and ex- 
hibitors' guests. For the remaining 
three days the full Personal Computing 
Show and Personal Computing College 
will be running. Over 80 hours of free 
seminars are planned. Contact John H 
Dilks III, Rt 1, POB 242 (Warf Rd), 
Mays Landing NJ 08330. 

August 29-31, Data Processing Oper- 
ations Management, New York NY. 
See July 17-19, Houston TX, for infor- 
mation. 

September 6-8, COMPCON Fall '78, 
Capitol Hilton Hotel, Washington DC. 
Sponsored by the IEEE Computer 
Society, this conference will cover 
computers and communications, inter- 
faces and interactions. Such topics as 
microprocessors in communications, 
multiple computer systems, advances in 
communications technology and many 
others will be discussed at this confer- 
ence. Contact Kenneth H Crandall Jr, 
COMPCON Fall '78, POB 639, Sil- 
ver Spring MD 20901. 

September 11-15, Coding and Informa- 
tion Theory, Georgia Institute of Tech- 
nology, Atlanta GA. See July 17-21, 
UCLA, for information. 

September 18-22, Digital Filters, Georgia 
Institute of Technology, Atlanta GA. 
See July 31-August 4, University of 
Toronto, for information. 

September 29-October 1, International 
Microcomputer Exposition, Dallas Con- 
vention Center, Dallas TX. This exposi- 
tion will be directed toward all levels of 
technology from the professional engin- 
eer to the beginning computer hobbyist. 
In addition to the seminars, a panel of 
experts will be available to answer 
questions. Contact Beverly Tanner at 
(214) 271-9311." 



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P.O. Box 60968 
Sunnyvale, CA 94088 
408-245-8855 




SERVICES 



luly 1978 e BYTE Publications Inc 1 73 



Continued from page 63 



X * 



M2 



M2 



Ml 



M2 



Tl I T2 I T3 1 T4 I Tl I T2 I T3 | Tl | T2 | T3 | T4 | Tl | T2 | T3 | Tl | T2 | T3 | T4 Tl j T2 



J ^ r 



J — ^ r 



J — \ r 



J ^ r 



"1^ 



"VJ" 



"A r 



"A_^ 



"Y^ 



X SELECT 



"A r 



1 r 



Y SELECT 



J V. 



J V. 



Y * 




EXTRA WAIT STATE 



Figure 3b: Ml, Tl IMl , Tl, one of the seven interprocessor T state alignments 
shown in table 1. Synchronization Is achieved after three clocfi cycles In this 
example. A complete discussion of the M and T states can be found in the 
Z-80 technical manual. (Note that, even though the arbiter activates the wait 
lines at periods during synchronization, this has no effect on the processors 
because the lines are not sampled until the falling edge of T2.) 



Inter -processor 
State Relationship 


Synchronization Pattern 
M1,T1/M1,T3 M1,T1/M2,T3 


Wait States 


T States Until 
Synchronization 


M1,T1/M1,T1 




V 





1 


3 


M1,T1/M1,T2 


V 




1 





3 


M1,T1/M1,T3 


V 













M1,T1/M1,T4 


V 







1 


6 


M1,T1/M2,T1 


V 







2 


7 


M1,T1/M2,T2 




V 


1 





3 


M1,T1/M2,T3 




V 












Table 3: Timing analysis for two Z-80 processors in parallel. The seven 
possible interprocessor state relationships are shown at left. The center 
column lists the two possible classes of operation for the parallel processors: 
the first (Ml ,T1 IMl ,T3) occurs when both processors are performing an op 
code fetch at the time of synchronization; the second is the case when one 
processor Is performing an op code fetch while the other Is performing a 
memory read or write. The wait states column indicates how many wait states 
each processor must undergo until synchronization occurs. Note that in two 
of the cases, the shared memory arbiter (see figure 2a) need not be employed, 
since the two processors fall into synchronization spontaneously. 



suit, enabling IC3b; ie: granting processor 
Y's request. 

System Timing 

In order to choose a memory that is 
subject to overlapping access requests from 
more than one processor, system timing 
must be carefully examined. Important 
considerations in this design include the 
control logic propagation delay and the 
"window size" provided by the processors 
for read or write accesses to the common 
memory. 

In the single processor system, the 
smallest memory access window of any Z-80 
instruction occurs during the op code fetch 
cycle. The effective length of that cycle is a 
few nanoseconds less than 1.5 clock cycles 
(1.5 <I>). However, the dual processor config- 
uration reduces the window size for two 
reasons: (1) the delay in processor selection 
(ie; the data gating signal) incurred by the 
control logic and, (2) the overlap of the 
memory request signals from opposing 
processors that is required to permit full 
speed operation by the processors. Further, 
the memory cycle time requirement 
becomes more stringent, accommodating 
from more than two clock cycles in a 1 pro- 
cessor system to less than one clock cycle in 
this system. 



174 



|uly 1978 O BYTE Publications Inc 



SHARED MEMORY 
ADDRESS BUS 



MAI5-MA0 



NOTE: 

MAIS IS NOT CONNECTED 




The clock that drives the processors 
operates at 2.5 MHz, defining a basic cycle 
time of 400 ns. With this information it is 
now possible to calculate the operating char- 
acteristics required of the shared memory. 

As stated earlier, the memory access 
window depends on the control logic switch- 
ing delay and the request signals overlap. It 
has been shown (see figure 3) that the 
smallest window occurs at times of bus 
request conflicts, and that this window has a 
length of one clock cycle. The equation, 



then, for actual window length is: 

La = *-S"T^-Td 

where: 

$ = 400 ns (1 clock cycle) 

6 = maximum delay in falling edge of 

MREQ 
T = maximum propagation delay of 

control logic 
Tj = maximum propagation delay of 



Figure 4: Block diagram of 
the shared memory. The 
memory is arranged in a 
square array of 64 static 
programmable memory 
integrated circuits with 
4096 bits per circuit. 



decoding logic 



luly 1978 © BYTE Publicilions Inc 1 75 



Examining the control logic timing shown 
in table 2, we observe that the maximum 
timing delays from either MREQ line going 
activ e until th e arbiter sets the correspond- 
ing SELECT line active are as follows: 



IC In Signal 
Path 


Maximum 

Propagation 

Delay (ns) 


74S04 
74S10 
74LS126 

Total Arbiter 
Delay: 


5 

5 

+18 

28 ns 



Substituting into the equation for L , we 
obtain: 



L = $-5 

a 



Tc-Td 



= 400-20-28-Tj 
= 352 -Tj ns 

The s witching delay of the decoding 
logic, T^ (SELECT active until the memory 
receives the signals), further reduces the 
memory access window. Referring to figures 
2b and 4, the signal path Tj is: 

Tj = 7408 + max [74S1 57 (select), 
74S157 (enable)] + 74S1 38 
= 19 + max [15, 11] + 12 
= 46 ns 



Finally, 
L, = 



352 -T^ 
306 ns 



This allows plenty of time for a memory 
access operation; so much time, in fact, that 
we do not need the faster and more expen- 
sive bipolar programmable memory. 

We must also consider the memory cycle 
timing (L ), reduced by this two processor 
system to "l> — 6 : 

L = $-6 
= 400-20 
= 380 ns 

It is good design practice to calculate 
delays in the system using the maximum 
time figures rather than typical ones, and to 
adjust the results by including a safety mar- 
gin. Accordingly, we specify the following 
requirements for the shared static program- 
mable memory: 



• Access time 280 ns or less 

• Cycle time 350 ns or less 

Conclusions and Possible Applications 

The principle advantage of two (or more) 
parallel processors performing complemen- 
tary tasks is the cost savings. For example, 
let us say that we operate a packet switching 
network in which multiple microprocessors 
perform the relay functions of each node, 
such as the TELENET of Telenet Communi- 
cations Corporation. Our responsibilities 
include insuring data reliability (eg: using 
cyclic redundance coding (CRC), checksum, 
etc), doing format checks, and recognizing 
the destination of the traffic and routing it 
to another node in the network. Further, 
this service must be provided at high speed. 

Clearly, for one processor to perform 
these and other nodal functions without 
some delay, high performance and high cost 
systems would be required. Conversely, mul- 
tiple microprocessors could perform all of 
these tasks in parallel at a significant reduc- 
tion in cost. 

For the experimenter, a multiprocessor 
system doesn't appear to offer much beyond 
an interesting diversion in design engineering. 
As mentioned earlier, the benefit from this 
type of design is increased throughput (by 
virtue of the reduced per unit cost). This is 
an idea that has little significance for persons 
with a dedicated system. 

One possible application does come to 
mind, however. Many 8080 system owners 
are upgrading to the Z-80 for the expanded 
instruction set, but for some, direct replace- 
ment of a processor board is not possible. 
Why not consider adding a Z-80 with your 
current system acting as a front end? 
Admittedly, it seems like a bit of overkill, 
but it is an inexpensive way ($8 for the 
interface circuitry of this design) to upgrade. 
Of course, after installing another processor, 
the owner must write an operating system to 
accommodate the addition; but that's part 
of the continuing challenge to be found in 
the world of microprocessors." 



REFERENCES 

Z80-CPU Technical Manual, Zilog, 1 70 State St, 
Los Altos CA 94022, 1976. 



1 76 )uly 1978 © BYTE Publications Inc 



85/P =8085 + PASCAL 




The new 85/P programmer's work- 
bench from Northwest Microcomputer 
Systems Inc combines the throughput 
of the 3 MHz Intel 8085A and the power 
of PASCAL. 

Designed for the serious applications 
programmer, the system features include; 
8085A processor, a PASCAL compiler 
and interpreter, CP/M supporting BASIC, 



COBOL and FORTRAN, direct memory 
access, two Shugart floppy disk drives 
with 1 M bytes of online storage, 54 K 
bytes of 450 ns user available static 
programmable memory, a Hall effect 
keyboard with 103 keys, two serial ports 
(RS232C), two parallel ports (16 bits), 
and a 24 by 80 character 12 inch (30.5 
cm) video display, all enclosed in a 
single cabinet. 

The system provides the full PASCAL 
environment including a 725 line per 
minute compiler and interpreter, random 
and sequential files, a screen oriented 
editor, interactive source linked debug- 
ger, plus full documentation and a 90 
day warranty. Pricing for the complete 
system is $7495. A variety of other 
packages are available, including a screen 
oriented accounting package and a word 
processor, from Northwest Microcom- 
puter Systems Inc, 121 E 11th, Eugene 
OR 97401." 

Circle 602 on inquiry card. 



New 2708 Erasable Read Only 
Memory Programmer 



New 6800 Industrial BASIC 



?>„ ■■;,.., ill, 

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Wintek 4 K BASIC is a 6800 BASIC 
interpreter optimized for industrial 
applications. Features of the package 
include control of interrupts, direct 
memory read and write, assembly lan- 
guage subroutine capability and flexible 
lO. The package is oriented toward proc- 
ess control and monitoring. 4 K BASIC 
retains all the advantages of an inter- 
active high level language, including 
rapid coding and debugging, easy main- 
tenance, and advanced control structures. 

The interpreter may reside in pro- 
grammable memory or in programmable 



read only memory for instant power on 
operation. If the BASIC program is also 
stored in programmable read only mem- 
ory, the interpreter will immediately en- 
ter the RUN mode, allowing unattended 
operation in dedicated applications. 

4 K BASIC is available on cassette at 
$95 or in programmable read only mem- 
ory on a Wince read only memory module 
for $299. The source listing is available 
for $95. For further information contact 
Wintek Corp, 902 N Ninth St, Lafayette 
IN 47904. ■ 

Circle 603 on inquiry card. 




A new 2708 erasable read only mem- 
ory programmer has been announced by 
Smoke Signal Broadcasting, POB 2017, 
Hollywood CA 90028. Designated the 
POP-1, the unit lists for $149 and is de- 
signed to interface to the company's 
P-38-1 and P-38-FF erasable read only 
memory boards, which are SwTPC SS-50 
bus compatible products. Complete soft- 
ware is provided on audio cassette. An 
adaptive programming technique is used 
that allows most 2708s to be pro- 
grammed in 15 seconds. A separate self- 
contained power supply is used for the 
programming voltage insuring sufficient 
current capability to program erasable 
read only memory from any manufac- 
turer." 

Circle 601 on inquiry card. 



Text Processing System for 
Microcomputers 

The Diaspar Text System is said to be 
a package of four programs which form 
a commercial text processing system. 
Text files are stored on diskettes using a 
named file structure with passwords. Ac- 
cording to the vendor, hardware needed 
for this product is an 8080 based micro- 
computer with 32 K of main memory, a 
screen terminal, floppy disk and a print- 
ing terminal. Software required is the 
CP/M operating system and CBASIC run- 
time package. The system comes on 
standard diskettes with a user's manual 
for $195 from Diaspar Data Systems, 
POB 888, San Juan Capistrano CA 
92675." 

Circle 604 on inquiry card. 



July 1978 © BYTE PubNcations Inc 177 



Whafs New? 



Miniature Switching Power Supplies 



of INTEREST to DESIGNERS 



Keeping Connected 




Tlie new 2505 MODCON series is 
available in double row configurations of 



10, 20, 40, 60, 80 and 100. These modu- 
lar high density receptacle connectors 
are designed for board to board inter- 
connect applications. The connectors 
are easy to mount using box form con- 
tacts that mate with conventional 0.025 
by 0.025 wiring posts on 100 inch 
center to center spacing. The series 
operates in temperatures between —55 
to -H50° C. Operating voltage is 800 V DC 
at sea level; insulation resistance is 
5000 M n minimum at 500 VDC; current 
rating is maximum 3 A; and contact 
resistance is 10 mO at 3 A. Contact 
Stanford Applied Engineering, 340 Martin 
Av, Santa Clara CA 95050." 

Circle 629 on inquiry card. 



New Probe Extends AQ6800 
Microprocessor Analyzer to 6802 Use 




This buffered probe extends the 
capabilities of the AQ6800 Microproc- 



essor Analyzer to 6802 microprocessors. 
With the PRB68/02 probe, the AQ6800 
displays all address, data and status 
information of any 6802 microcomputer 
system, and provides direct user inter- 
action with all memory locations, 10 
ports, and internal microprocessor regis- 
ters. The probe clips directly to the 6802 
microprocessor chip in the system being 
tested. Interactive features include the 
ability to examine or modify the contents 
of all 6800 or 6802 internal registers, 
plus the program counter, manual or 
breakpoint program halt, single step 
operation, execution of single byte 
instructions independent of normal 
program flow and many other control 
capabilities. The probe is priced at $295 
and the AQ6800/02 system, complete 
with probe, is $1950. Contact AQ 
Systems Inc, 1736 Front St, Yorktown 
Heights NY 10598." 

Circle 630 on inquiry card. 



200 and 400 W Open Frame Switching 
Regulated Power Supplies 




The OL-200 is a four output unit 
which supplies 200 W of continuous 
power, -^5 V at 25 A (maximum) from 
one output, -5 V at 4 A, and ±12 V at 
4 A each. The OL-400 is a five output 
unit that is capable of supplying a 
continuous 400 W, ±5 V at 45 A from 
one output, ±12 V at 10 A each from 
two outputs, and -5 V and +24 V at 
4 A each from the remaining two out- 
puts. Each unit is capable under tran- 
sient conditions of handling three times 



the rated current. Both units can be 
adapted to provide voltages specified 
within ±70 V and up to 4 A per output 
for the OL-200 and 10 A per output for 
the OL-400. Input voltages are also user 
selectable. Both units will operate from 
either 115 VAC or 230 VAC and are 
equipped with brownout protection 
that allows them to operate without 
performance degradation at line voltages 
as low as 95 VAC (115 V option) or 
190 VAC (230 V option). Both power 
supplies can provide 16 ms of continu- 
ous power after full loss of input. Stan- 
dard features include an input EMI 
filter, a series thermistor that reduces 
input line surges at turn on, reverse 
voltage protection, and protection 
against system shorts. The OL-200 is 
priced at $248 and the OL-400 at $395 
in quantities of 100. Contact Boschert 
Associates, 384 Santa Trinita, Sunnyvale 
CA 94086." 

Circle 631 on inquiry card. 




Three 12 V, 15 V and 24 V units, 
with efficiencies from 75 to 85 percent, 
have been added to Gould's MMG line 
of 5 V, 25 W switching power supplies. 
The new units operate from 1 10 and 120 
V or 220 and 240 V ±10%, 50 or 60 Hz, 
and currents from 1.4 to 2.5 A. Optical 
coupling is used to provide 4 kV rms 
insulation (5.7 kV peak) between input 
and output. Units can be used in series 
or parallel operation without special 
interconnections. 

Remote sensing is available from 
terminals on the printed circuit board 
adjacent to the output connections for 
control of voltage at the load instead of 
at the power supply. Standard features 
include overcurrent and overvoltage 
protection. Gould MMG switching power 
supplies carry a 5 year warranty. 

The units cost $135 in quantities of 
one to nine. Contact Gould's Electronic 
Components Division, 4601 N Arden Dr, 
El Monte CA 91731." 

Circle 632 on inquiry card. 



It's Late in the Learning Curve for 
8080s 




National Semiconductor Corporation 
has announced across the board price 
reductions for its version of 8080A 
microprocessors. The price of National's 
plastic package INS8080AN is now listed 
at $9.98 in quantities of 1 to 24, reduced 
from a previous listing of $15.50 each. 
In quantities above 100, the device has 
been marked down by one third, from 
$10.80 to $7.10, as quoted in National's 
latest OEM price list. Contact National 
Semiconductor Corp, 2900 Semiconduc- 
tor Dr, Santa Clara CA 9505 1 .■ 

Circle 633 on mquprv card. 



178 



luly 1978 ©BYTE Publicalions Inc 



5 PLETE SATISFACTION IS OUR GUARANTEE YOUR COMPLETE SATISFACTION IS OUR GUARANTEE YOUR COMPLETE SATISFACTION 



Huge Discounts! 

HOBBY WOBLB ELECTBONICS 

Savings up to 70% on major brand IC parts and computer 
kits. For complete IC listings write for our catalog. 





-^KITS 






WAMECO 


S-lOO RC. 


Boards 






8K RAM 




28.00 




8080 CPU 




28.00 




12-Slot Mother 






Board 




33.00 


THACA AUDIO SlOO PC. 


Boards 






8K RAM 




28.00 




Z-80 CPU 




28.00 




2708/2716 EPROM 





<?" 







Boards (New) 28.00 | 
W/W Prototype 

Board (New) 25.00 | 

I SOLID STATE MUSIC S-100 Kits & 

Bare Boards 
IMB6A8K Kit 129.951 

ISTATIC RAM Bare Board 25.95 | 

|mB7 16K STATIC RAM 

Kit 435.00 I onrn^c 

Bare Board 25.95 DUUKo 

|MB8 8K/16 K EPROM The Basic Workbook $ 

USES 2708's Programming Proverbs 

Kit Less EPROMs 75.95 Discovering BAS IC 
COBOL with Style 
Advanced BASIC 
Standard Dictionary of Computers 

& Information Processing 
Game Playing with Computers 
Game Playing with BASIC 
Minicomputers 
Microprocessors 
Digital Experiments 
Digital Signal Analysis 
Digital Troubleshooting 
110 CMOS Digital IC Projects 
400 Ideas for Design. Volume 2 
Analysis and Design of 

Digital Circuits and 

Computer Systems 
Telephone Accessories * 

You Can Build 
Basic Electronic Switching for 

Telephone Systems 
Basic Carrier Telephony 






'^C/f 






74L$00 TTL 



74L$00 

74L$02 

74LS04 

74LS08 

74L$10 

74LJI4 

74LS20 

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74L$32 

74L$37 

74Lt38 

74L$42 

74L$47 

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74H73 

74L$74 

74L$75 

74L»76 

74L$86 

74LS90 

74L$92 

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74LS114 

74LJ125 

74LS126 

74LS132 



74L$138 

74L$139 

74L$15t 

74L$153 .66 

74L$154 1.00 

74LJ157 

74LS160 

74LS161 

74L$162 

74L$163 

74L$164 

74LS174 

74L$175 

74LS190 

74L$191 

74LS192 

74LJ196 

74L$197 

74L$221 1.06 

74LJ257 

74L$258 

74L$266 

74LJ283 

74L$365 

74L$366 

74L$367 

74L$368 

74L$386 

81LS95 

51L$96 

eiL$97 

81LS98 



.65 



.82 
82 



.98 



.80 



55 



5.S0 
6.95 
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(Continued) 

8080 Machine Languages 

Programming 6.96 

Robots At Your Doorstep 6.95 

BEGINNERS BOOKS 

9.95 



KITS 

I SOLID STATE MUSIC 
IVBIB VIDEO INTERFACE 

Kit 129.95 

Bare Board 25.95 

I RF Modulator TV-1 Converts Video 
Output to RF For TV antenna 
terminals, complete Kit 8.95 

I NEW FROM CYBERCOM DIV OF SSM 
MB8A-2708 16K EPROM with 

Vector Jump Kit 85.00 

OB-1 Vector Jump & Prototype 

Kit 49.00 

Board 25.95 

1 104 2 + 2 I/O Kit 139.95 

ISYNTHESIZER SB-1 MUSIC 
Kit with 

Software 145.<XI 

|MT-1 15-Slot Mother 

Board 39.95 

XB-1 EXTENDER BOARD 
Bare Board 8.99 

SSM 8080 MONITOR VI 
ON 2-2708 47.00 

ON 8-1702A 47.00 



Beginning BASIC 

Home Computer Beginners 

Glossary and Guide 
Basic BASIC 
Introduction to BASIC 
Home Computers; 210 Questions 

and Answers 

Volume 2: Software 
Microcomputer Dictionary 

and Guide 
Microprocessor Basics 
Home Computers: 210 Questions 

and Answers 

Volume 1; Hardware 
Understanding Integrated 

Circuits 
Semiconductor Circuit Elements 
Fundamentals and Applications 

of Digital Logic Circuits 



6.95 
8.95 
8.95 



19.95 
10.95 



4.95 
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74XX 




SUPPORT DEVICES 



6820 
6850 
8212 
8214 
8216 
8224 
8228 
8226 
8238 




8.00 
8.00 
3.45 MEMORY 

8.00 1702A 3.75 

3.75 2708 11.50 

3.50 2716TI 22.50 

6.25 21L02 450ns 1.25 
3.85 21L02 250ns 1.60 
7.95 2114 8.50 

MICROPROCESSOR 
8080A 11.50 

24.95 
34.95 
16.50 



''rNew)25Pin— DSub 
miniature Solder Tail 
Male 3.00 
Female 3.50 

100 PIN EDGE CONNECTOR. 
Imsai spacing 3.50 (New) 




7400 
7401 
7402 
7403 
7404 
7405 
7406 
7407 
7408 
7409 
7410 
7411 



7420 
7423 
7425 
7426 
7427 
7430 
743Z 
743 7 
743S 
7439 
7440 



7482 

7483 

7485 

7486 

7489 

7490 

7491 

7492 

7493 

7494 

7495 

7496 

74107 

741L)9 

74121 



74132 
74141 
74145 
74150 
74151 
74153 
74154 
74157 
74161 
74163 
74164 
74165 
74170 
74173 
74174 
74175 
74176 
74177 
74180 
74181 
74190 
74191 
74192 
74193 
74195 
74221 
74251 
74365 
74366 
74367 
74368 




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IS OUR GUARANTEE YOUR COMPLETE SATISFACTION IS OUR GUARANTEE YOUR COMPLETE SATISFACTION IS OUR GUARANTEE 



Circle 170 on inquiry card. 



BYTE )uly 1978 179 



Circle 25 on inquiry card. 



ATW< 



• I#ll 



ENTERPRISES 



KITS 



Available assembled and tested $89.95. 



$ 79.95 4K RAM 

$ 1 29*95 4K PROlvl Bipolar 512x8 Proms 93448/6341 . 

$149*95 8K EPROlvl Needs onlv4K space 27I6. 

$ 59*95 DIGITAL I/O 8 parallel ports plus le interrupts. 

$ 99*95 ANALOG IN 32inputs, 8 bits, 100 microseconds 

$ 49*95 PROM PROGRAMMING 

$129*95 SERIAL I/O 



I DID YOU 
I KNOW . . . 

-| BIG SALE 

I 1 each board: 



Digital I/O 

Eprom programming 

8K Eprom Board (without 2716's) 



1 
I 

-| REGULAR PRICE 



7 serial ports, fully software controlled 
To 500 baud. 



J $139.85 

Burns4 | JUNE ONLY 

Can copy to 3. I . 

-I $100.00 

I Extra zero insertion force sockets $5.00 



MOTHER BOARD 

8 SLOT 44 PIN BUS 

50 Pin Edge Connector 

Mother Board $20.00 ea 
Connectors 2.50 ea 

Card guides for above $10.00 per set. 



MAKE CHECK OR MONEY ORDER PAYABLE TO: 

Kathryn Atwood Enterprises 

P.O. Box 5203. Orange, CA 92667 

Discounts available at OEM quantities. For orders less than $25 total, add $1 .25 
for shipping. California residents add 6% sales tax. Estimated shipping time 2 
days ARO with money order. For checks allow 7 days for check to clear. 



Beckian Enterprises All Prime Quality — New Parts Only — Satisfaction Guaranteed 



EPGE CARP COmiaC^ : GOLV PLATEV . 

BODY: Non brittle, solvent resistant, high temperature G. E. Velox. The finest elec- 
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ALTAin TYPE 



Contact Ctrs. .125: Row Spacing, 
Dip Solder $4.00 ea. 



.140 



50/100 Dip Solder $4.00 ea. 5 pes, 

IMSAI TVPE: Contact Ctrs. .125: Row Spacing, .260 



50/100 
50/100 



Dip Solder 
Wire Wrap II TurnI 
(3 Turn) 



$4.25 ea. 
$4.25 ea. 



5 pes. 
5 pes. 



IMSAI Card Guides " .25 per pair to IMSAI Prices 

Note Also good for CROMEMCO, 

OTHER COmECTORS AVAILABLE 
.100" Contact Ctti: .140" Row Spacing . 



15/30 Solder Eyelet 

22/44 Dip Solder 

22/44 Wire Wrap (3 Turn) 

40/80 Wire Wrap 13 Turn) 



$2.30 ea. 
$2.75 ea. 
$2.50 ea. 
$4.00 ea. 



5 pes. 
5 pes. 
5 pes. 
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$3.80 ea. 



$4.00 ea. 
$4.00 ea. 



$2.10 ea. 

$2.40 ea. 

$2.20 ea. 

$3.70 ea. 



Note: llJAe Wiap S^xiclnQ -16 .200" (Row Spac-cng) 
.15b" Contact CVii: .140" Row SjxiCAjig . 



18/36 Dip Solder 

22/44 Dip Solder 

15/30 Wire Wrap (3 Turn) 



$2.25 ea. 
$2.50 ea. 
$2.00 ea. 



5 pes. 
5 pes. 
5 pes. 



156" Contact Ctu: .200" Row S]XLclng . 



22/44 
36/72 
15/30 
18/36 
36/72 
43/86 



Wire Wrap 13 Turns) 

Wire Wrap (3 Turns) 

Dip Solder 

Dip Solder 

Dip Solder 

Dip Solder (6800) 



$2.80 ea. 
$4.00 ea. 
Sl.eOea. 
$1.95ea. 
$4,00 ea. 
$4.90 ea. 



5 pes. 
5 pes. 
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5 pes. 
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$2.00 ea 
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25 PIN VB TVPE SUBUINTATURE CONNECTORS . 

CANNON: Gold Plated. The Best You Can Buv. 

DB25P Male Plug 
DB25S Female Socitet 
DB 51212-1 Hood. (Grey) 
DB 51226-lA Hood. (Blaclr) 
D 20418-2 Hardware Set 

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Complete Set includes: 1 pe. DB25P: 1 pe. DB25S: 

1 PC. Hood of your choice Grey or Btaelt, 

1 Set $6.50 ea. 5 Sets $6.25 ea. 

Note: For D 20418-2 Hardware Set. add $0.75 ea. 



$2.60 ea. 


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5 PCS. 


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5 PCS. 


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$1 lOea. 


6 pes. 


$1.00 ea 


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27 OS - PRIME 

(450 nS) 
$14.00 ea. 



BOSOA - PRIME 

$9.40 ea. 



I.e. SOCKETS: VIP SOLVER 

Low Profile. 
14 pin.a 16 pin. $0.16 ea. 

HEAT SHRINK TUBING 

I/8"shrinl<sto 1/16" I.D. $0.35 per ft. 

CABLE TIES 

314" and S'/i" $0.03 ea. 

WRITE FOR LARGER QUANTITY VISCOUNTS 
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OldeA Tfiom: 



Beckian Enterprises 
P.O. Box 3089 Simi, Calif. 93063 



180 BYTE July 1978 



Circle 30 on inquiry card. 



FOR AL 

211-02 (450ns) 
Static Rams 
100 SI $1.10 ea. 



Z-KU 

Microprocessor 
5 @ $20.00 ea. 



CUSTOMERS EXCEPT CALIF. CALL TOLL FREE 800-421 5809 



1702A 
E— PROM 
8 S> $3.75 



8224-4 

Clk.Gen.&Dvr. 
25 @ $8.75ea. 



6502 

Microprocessor 
5 @ $11.00 ea. 



410D (200ns) 
Static Ram 
100 @ $8.75ea. 



MICROCOMPUTER COMPONENTS 

MICROPROCESSOR-S "'^^^ "^HER COMPONENTS 



F8 
Z8 

zaoA 

CDP1802CD 

26S0 

AM2901 

6S02 

6B0O 

SB02 

8008-1 

8035 

80B0A 

8085 

TMS9900TL 



16.95 
12.00 
28.00 
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24.95 
22.95 
11.95 
18.95 
25.00 
9.9 5 
22.00 
11.95 
27.00 
75.00 



8080A SUPPORT DEVICES 

8212 3.50 

8214 9.00 

8216 3.75 

8224 3.50 

8224-4 9.95 

8236 3.95 

8228 7.95 

823B 7.50 

B251 9.95 

8253 21.95 

8255 21.95 

825 7 21.95 

8259 21.95 

B275 75.00 

8279 20.00 

FLOPPY DISC CONTROLLER 

17718 55.95 

1 7 7 1 a-0 1 5 7 .9 5 

KEYBOARD CHIPS 

AYS-2376 13.75 

AV5— 3600 13.75 



PROM'S 

1702A 

2704 

2708 

2716 

2716 intl 

2758 

O3601 

D3604 

5203 AQ 

5204 AQ 
6834 
6834-t 
82S2 3B 
82S129B 
B223B 

6800 SUPPORT 

6810P 

6BB10P 

6B20P 

6821 P 

6828P 

6834 P 

6850P 

6852P 

e860P 

6B62P 

6871 P 

6875P 

6880P 



4.00 

15.00 

12.00 

30.00 

38.00 

26.60 

4.50 

13.00 

5.00 

7.50 

17.50 

14.95 

4.00 

4.2 5 

3,50 



4.95 
6.00 
7.50 
J. 50 
11.25 
16.95 
9.75 

1 1.75 
10.00 
14.50 

2 8.00 
8.75 
2.50 



Z80 SUPPORT DEVICES 

3881 12-95 



STATIC RAMS 
21L02 1.51 



21L02 I 

21 Lj02 j 

410D 

1101 A 

2101-1 

2102 

2111-1 

21 12-1 

2114-3 

2125L 

2147 



) 1.7S 1.60 

10.75 lO.OO 

1.00 .90 

2.95 2.75 

1.25 I. IS 

3.95 3.50 

2,95 2.80 



1.18 
1.25 
1.50 
9.25 
.80 
2.60 
1,00 
3.2 5 
2.69 
9.25 



31 L 

3 106 

3107 

TMS-4 04 4 

4200 A 

TMS-4045 

5101 

74C89 

7489 

74S201 

PBlOl 

P8155 

P8156 

8599 

9102BPC 



2.35 
3.70 
3.70 
9.00 



37.50 
2.50 
3.9 5 
3.95 
9.95 

12.95 

11.00 10.00 
8.30 7.40 
3,25 3.05 
2.25 2.10 
4.50 4.00 
4.20 3.40 

17.00 14.00 

21.00 18.00 
1.8B 1.7 5 
1.6 5 1.4 5 



2.00 
3.25 
3.25 
8.95 

9.25 
7.25 
2,85 
1.90 
3.75 
2.B0 



CHARACTER GENERATORS 

2513 6.75 
2513 5v upper 9.75 
2513 5v lower 10.95 

2516 10.95 

MCM6571 10.95 

MCM6571 A 10.95 

MCM6574 13.25 

MCM6575 13.25 

WAVEFORM GENERATOR 

8038 3.50 

MC4 24 2.2 5 

566 1.50 

DYNAMIC RAMS 

4160/4116 32.00 

1103 1.00 

2104 4.00 

2107B 4.25 

210 7 8-4 3.9 5 

TMS4050 4.00 

TMS4060 4.50 

TMS4070-2 32.00 

4096 4.00 

4116/4I6D 32.00 

MM52 7 4.50 

MCM6605 S.OO 

USRT 

S2350 10.75 

UART'S 

AYS 101 3 A 
AV5-10I4 A 
TR1602B 
TMS6 01 I 
IM6402 
< M6 4 3 



5. 25 
8.25 
5.25 
S.9S 
10.80 
lO.BO 



JADE 8080A KIT 

$100.00 KIT 

BAHE BOARD $30.00 



N8T20 
N8T26 
NgT9 5 
N8T96 
NBT9 7 
N8T9 8 
8 1 LS9 5 
81 LS9 7 
1488 
1489 
D3205 
D3207 A 
D3208A 
03 211 
63 2 22 
B324 2 
03 245 
C3404 
P3408 A 
P4201 A 
MM5320 
MMS369 
TMS5501 
OM81 30 
OMB131 
OMSB3 3 
OM8e35 
DM8B3 7 
MKS0240 
MK50250 



3.39 
2.10 
1.35 
1.35 
1.35 
1.35 
2.00 
2.00 
1.75 
1.75 
4.00 
4.55 
14.20 
10.00 
9.75 
10.15 
5.60 



6.75 

.2.00 

5.20 

7.50 

1.9 

24.9 5 

2.9 

2.75 

2.50 

2.50 

1.7S 

20.0 

15.00 



2708 (4 50 ns) 

E— PROM 

8 @ $11.00 ea. 



4096 

Dynamic Ram 
100 @ $3.50 ea. 



E-PROM BOARDS 



MM 16 I16N uiri 1/ 

flAWN'ROM IIGK ,1 
E I'HOMI 



S9*»l)0 
S99'jO 

S99 0n 

SI woo 



TJ-l 



Convert T,V. sel to 

Video Monitor. 

KIT S8.95 



STATIC RAM BOARDS 



8K 



$189,95 
$149 75 
$169 95 
$125 00 
2500 



2S0ns ASSEMBLED & TESTED 

450ni ASSEMBLED 8. TESTED 

250ns KIT 

450oi KIT 

BARE BOARD 

6800 ADAPTER lo S100 Syttem 

KIT S12.95 

16K 

2S0ni ASSEMBLED & TESTED $435.00 

4S0ns ASSEMBLED 8. TESTED $380 00 

450m KIT $335,00 

32 K 

2&0n<i ASSEMBLED S. TESTED $850.00 

450nj ASSEMBLED & TESTED $775.00 

450ni KIT $675,00 

DYNAMIC RAM BOARDS 

On ba«ril R*ti«(h pow»r u provided «iib "u *»>t 
iiim oi cycle itailing iH)uir«l 
■ 8VDC 400MA DC -tSVOC 400MA DC jnd 

I8VOC SOMA DC 



EXPANDABLE 

8K (375nj| KIT 

16K (375ns) KIT 

24K I375nil KIT 

32K (375nO KIT 

EXPANDABLE 
16K (375ni) KIT 
32K (375nil KIT 
48K I375nil KIT 
&4K (375nil KIT 



$151-00 
$259 00 
$367.00 
$425-00 



$281 00 
$519.00 
$757.00 
$995.00 



MOTHER BOARD'S - S 100 Style 
13 slot - w/front panel ilot 
BARE BOARD $35.00 

KIT $96.00 



22 slot 



$149.95 



ASSEMBLED 8i TESTED 



THE PROM SETTER 

WRITE S, READ 

EPROM 

1702A - 2708 - 2716 

5204 - 6834 

- Plugi n.<tflly o'lO vUu' ALTAIR iWSAI Com^iiK 
' lociuiKs Ma<n Modiiip Bovrt af^a t'lri CPRO' 

Soch'i Un.i 
■ The EPHOM Soclir' U...I is coii.in lurt ii) "»■ C.m' 

pure, through ., 26 O'" connecio^ 
' Prograrnmtf>g fs ac<:Ofrtpii\t\ed bv '*^*' Ci*"iijv*i»*f 



KIT S210.00 

ASSEMBLED $376 00 



KIM-1 

ASSEMBLED & TESTED $245.00 



MEMORY PLUS 
for KIM-1 
8K RAM I21L02) 
8K EPROM 

ASSEMBLED & TESTED 
$245.00 



211J02 (250ns) 
Static Rams 
100 @ $1.36 ea. 



4200A (200ns) 

Static Rams 

25 S> $10.00 ea. 



Z— 80A 

Microprocessor 
5 @ $2 5.00 ea. 



74LS36 7 
Hex Buffer 
100 @> .70? 



jadeZ80„,, 

-Mth PROVISIONS tor ^\ \ 

ONBOARD 770B md POWER ON JUMP 

$135.00 EA.™« 
$149.95 EA. — 

BARE BOARD $35.00 



Z80 "UPGRADE" KIT 

Chjnge your JADE 3MHi Z80 lo a 4MHi uersn 
wiih lhi5 simple kii 

only $17.95 with trade 
$49.95 purchase. 

To trade, you must give ui youf 2MHi 280 chi| 

and B234 clock dt.ve< 

The UPGRADE KIT'' mcludei 

ZSOAchip. 1.8K tesiiior 

8224 4 clock dii«er 20 p(. capadtoi 

36IV!Hf crystal 



COMPU.TIME 

SlOO BUS COMPATIBLE ^ ' lUU 

TIME & CALENDAR 

MJcroprocejjors need the power that a leal time cinck 
can oHet Oaie and time becomes msiantlv available 
COMPU/TIME does not have lo be mniaiijed eue'v '"^^ 
the system IS powered up It possesses a crysial connolied 
time base to obtam superior accurKy and has two seiable 
coincideriee counters. Time, date, and counterj are set 
via software. 

COMPUTATIONAL FUNCTION 
Microprocessors need to be comp'imenied by hafdwaie 
arithmetics to free up memory pages dedicated to float 
ing point routines and mathmaiical software COUPU/ 
TIME provides a 40 function calculator anay so f'lai 
algebraic, Inqonometnc, basic aithmetic proMems can 
be solved wiihotit the need of ripveloping saplnsiicated 
software. a. 



COIiAPUTIME CTl( 

COMPU <inl, C101 

TIME only T101 

COIUIPU'TIME PC e 



iuy It Your Way 

$199 KIT $245 

$149 KIT $189 

$165 KIT $205 

d o„[y $80 



JADE VIDEO 
INTERFACE KIT 

FEATURES $99.95 

S 100 Bus Compatible 

32 or 64 Characters per line 

16 lines 

Graphics (128 x 48 matrix) 

Parallel & Compositive video 

On board low-power memory 

Powerful software included for 
cursor, home, EOL, Scroll Graphics/ 
Character, etc. 

Upper case lower case & Greek 
Black on- white & white on-black 



full ASCII 
PROFESSIONAL KEYBOARDS 

full 13b Chardcle- ASCH' 
Ir.-Mode MOi Entodmg' 

M03 DIi TTL Compatabic Om'p-.' 

T*o-ke/ Rollover' 

level and ^^.i^e ^irob«< MODEL 

Sh,(T and Alpha Lock' 755 

Selec'able Panty 



Negai 



Logu 



156 keys) 



PRICING INFORMATION 
Model 756 (•siembledl i75 9J 
Model 756K (kii) 64 95 

Model 703 Er>closure 29 95 

Model 710 Numeric Pad 9 95 
Model 7S6MF Mig Fr«n^e 8 95 



8212 

8 Bit I/O Port 

?5 @ $3.00 ea. 



74LS368 
Hex Inverter 
100 @ .70^ ea. 



4116 (200ns) 
16 K Dyn. Ram 
16 @ $24.00 ea 



2513 (5v) 
Character Gen. 
5 @ $9.00 ea. 



REAL TIME CLOCK FOR S-IU BUS 

1 MHZCrvitai Otcillator 

Two indepenbeni interrupts 

One interrupt uiM 16 b<t counter in 

10USEC steps 

Other interrupt is <n decade stept trom 

100USEC to 10 sec. 

Both software programmable 

Board can be selected bv 1 28 device 

code pairs 

Complete documentation includes sott- 

vwre to dispiav nme of dav 

Double sided solder mask 

Silk screen parts layout 

JG-HT ASSEMBLED & TESTED S179. 

JG- RT KIT $124,95 

SARE BOARD miih Man.isl S30.00 



TARBELL 
CASSETTE INTERFACE 

• Plugs diieclly into you. IMSAl or ALTAIR " 

• FaiiesrtTanslerraie 187 (standard) to 540bytes/second 

• Extremely Reliable — Phase encoded (self clocking) 

• 4 Extra Stalus Lines. 4 Extra Control Lines 

• 37 page manual included 

• Device Code Selectable by DlP-switch 

• Capable o( Generaling Kansas City tapes also 

" No modilication required on audio cassette recorder 

JADE KIT* S99.95 ASSEMBLED $175.00 

•16 monlh warranlv trom JADEI MANUAL S4 00 



JADE PARALLEL/SERIAL 
INTERFACE KIT 
sioo S124.95 KIT 

2 Serial Interfaces with RS232 

interfaces or 1 Kansas City cassette 

interface. 

Sena! interfaces are crystal controlled. 

Selectable baud rates. 

Cassette works up to 1200 baud. 

1 parallel port. 



DATA COMMUNICATIONS ADAPTER 



* Comgletelv compatible 
SOL" Of other SlOOr 
Trademarkiot 'MITS, 

• Oesigoect for um on tlie 



ilTh your IMSAl. ALTAIR* 
icrocomputari 
'ProceiiOr T«chnotogv 
lial IBlaphona ar TWX 
:ated Irnei, m>Bti ill 
ed wiihaCBTcouplar. 



FCC regulations when i 
• All digita' rnodulation and damodulation with on 
board cyrxal dock and procition dlttr rnean thai 
NO ADJUSTMENTS ARE REQUIRED 

• Ball 103 iianda'd fraguartciai 

• Automated dial (pulsed) and •ntwar 

• Originata and answer mode 

• 1 to O' 300 BPS ipee<l lelKt 

■ Complaia te" lasi capability 

■ Character langtfi , stop bit, and parity 

• 90 day warranty and full documentation 



PRICES: BABE BOARD ; 
Ass^mblpil (48 h 
JG OCA KIT 



S49.95 
$279.95 
$159.95 



NUMBER CRUNCHER 

The CT200 is a number onenied microprocessor intended 
lor use in those applications that repuire fast versatile 
mathematical solutions. 

THIS IS NOT A CALCULATOR CHIP, THERE ARE. NO 
KEY DELAYS 

The CT300 tias a unique architecture that is designed lo 
be a TASK piocessmg system within a system. This 
unique architeclute will allow the CT200 to work and run 
with ANY SIOO BUS microp-ocessor system It .s 
completely cnmpalible with Z80, 4MHZ version also. 
8080. 6800, 650? microprocessor A micro incoded 
instruction set allows programming in a calculatoi like 
language. The instruction set includes a full set of test 
and branch instruclions. AM decoding of SIOO bus 
signals (for select oi control funclionsl is performed with 
strobed latches to el'imtnate the possiljilitv of glitches 



Includes - Maniidl, 



PRICE: $249.00 
ASSEMBLED & TESTED, 



CONNECTORS 
DB - 25P S3. 00 
DB - 25S S4.00 



COVER 



$1.50 



44 Pm 

44 Pm 

86 Pin 

86 Pm 



PC & EYE 

WW 

16800) PC 

(COSUAC ELFI 
PC 
100 Pm - (Altatrl PC 
100 Pin - (Imsai) PC 
100 Pm - (Imiail WW 



$1.95 
$2,50 
$5.00 
$5.00 

$4.50 
$3.75 
$4.25 




Computer Products 

5351 West 144ih Street 
LAWNDALE, CALIFORNIA 90260 
(213) 6793313 

RETAIL STORE HOURS Monday Pndav 9-7 
Saturday 9-5 
Discounts available at OEM quaniities ADD $1,50 
under 10 lbs. tor shipping. California residents add 

6% sales tax. 

NEW CATALOG NOW AVAILABLE 



Circle 195 on inquiry card. 



BYTE July 1978 181 



Whafs New? 



PERIPHERALS 



Floppy Controller Uses New 
Motorola Chip 



Parallel and Serial lO 




A new peripheral board, called the 
Bit Streamer, is now available in assem- 



bled or kit form from Vector Graphic 
Inc, 790 Hampshire Rd, Westlake Vil- 
lage CA 91361. According to the com- 
pany, the Bit Streamer combines two 
parallel input and output ports, and a 
serial 10 port using an 8251 program- 
mable universal synchronous or asyn- 
chronous receiver and transmitter 
USART. One parallel port also can be 
used as a keyboard input port. The 
USART is designed to interface easily 
to an S-100 bus structure and is capable 
of being configured for a wide variety of 
communication formats. The price is 
$195 assembled and $155 for the kit. 
Technical data covering the Bit Streamer 
and other products may be obtained 
from the company.* 

Circle 624 on inquiry card. 



A New Audio Cassette Interface 





W c'^^^^^^^ 



This standard PerCom CIS-30+ inter- 
faces with the MITS 680b computer. 
The unit interfaces two cassette record- 



ers and a data terminal to a microcom- 
puter using the 6800 processors. It pro- 
vides user selected data rates of 300, 
600 or 1 200 bps. The two cassette inter- 
facing circuits are independent and si- 
multaneous dual tape operations are pos- 
sible. Optional program control of re- 
corders is available. Cassette data record- 
ing is done using the Kansas City Stand- 
ard (bi-phase-iVl, double frequency). The 
data terminal communication mode is 
full duplex. The MITS 680b read only 
memory monitor may be used for load- 
ing running programs, except for flip- 
ping the tape switch to on for program 
loading. The CIS-30+ sells for $79.95 in 
kit form, and $99.95 assembled and 
tested. An instruction manual is includ- 
ed. Contact PerCom Data Company, 318 
Barnes, Garland TX 75042." 

Circle 625 on inquiry card 




The new Motorola MCM 6843 floppy 
disk controller integrated circuit has 
been incorporated into a low cost but 
versatile floppy disk controller. The 4'/2 
by 6/2 inch (11.4 x 16.5 cm) module in- 
terfaces to any full size or minifloppy 
disk drive. The module supports both 
hard and soft sectoring, IBM 3740 or 
user programmable read and write for- 
mat, automatic CRC generation and 
checking, and programmable step and 
settling times. The price is $1 99. Contact 
Wintek Corp, 902 N 9th St, Lafayette 
IN 47904." 

Circle 627 on inquiry card 



Moving Head Disk Controller for 
LSI-11 Systems 




Add a Programmable Scientific 
Calculator to Your System 



0Si 


k 


T 




^^^ 


c 


^B^^^ m^y^ 


^^ 



This new microcalculator. Model 85, 
is intended for operation with an 8 bit 
microprocessor. The Model 85 requires 
only +5 V for operation and interfaces 



with the microprocessor thru an 8 bit 
bidirectional lO port. Each entry that 
would normally be made by a key is 
replaced with an 8 bit instruction from 
the microprocessor. The number of in- 
put instructions is not limited, restricted 
only to the user program or the amount 
of memory in the microprocessor sys- 
tem. Instruction entry to the microcalcu- 
lator is under microprocessor software 
control. It accepts instructions, provides 
a means to detect busy status, and out- 
puts the 14 digit display back to the 
microprocessor for storage or display. 
Complete software for controlling the 
microcalculator in both read and write 
modes requires less than 256 bytes of 
microprocessor system memory. The 
Model 85 has scientific calculation capa- 
bilities for handling scientific engineer- 
ing, mathematical or statistical prob- 
lems. Priced at $189 from Artisan Elec- 
tronics, 5 Eastmans Rd, Parsippany NJ 
07054." 

Circle 626 on inquiry card. 



The PX-C45L moving head disk con- 
troller enables you to add up to 40 
megabytes of storage to DEC PDP-11/ 
03, V03 Systems. It is Q-BUS com- 
patible and equipped with a 5 or 10 
megabyte disk drive. The controller is 
compatible with RT-11, FORTRAN, 
BASIC and other LSI-11 software. When 
used with a 5 megabyte disk drive, the 
removable media is interchangeable with 
DEC RK05 disk media. The unit is sup- 
plied in a 19 inch (48.3 cm) rack mount- 
able 5!4 inch (13.3 cm) chassis complete 
with bootstrap loader, +5 V, 25 A power 
supply, slides, cardcage assembly fans 
and a 5 or 10 megabyte disk drive. An 8 
foot (2.4 m) flat cable extends to the 
PDP-11/03 Q-BUS and three prewired 
Q-BUS 10 slots are available for user 
peripheral devices. The PX-C45L may be 
purchased separately or as part of a 
complete disk system. Contact Xylogics 
OEM Components Group Inc, 42 Third 
Av, Burlington MA 01803." 

Circle 628 on inquiry card. 



182 



July 1978 ©BYTE Publicilioni Inc 



Circle 1 15 on inquiry card. 



lectrolabs- 



Educational Grade VIDEOTAPE Special: 72x2400' 20 boxes/$125.00 



The "Pro" fully encoded ASCII Keyboard by Cherry. Auto RE- 
PEAT feature, 5 special function keys. 300mA/5V. (Shown as 
mounted in 'The Case' . Below) $119.00, 3/99.00, 10+/89.00 



USED SYLVAN/A 
12" MONITORS 
You Fix: $24.95 
Working: $69.95 
Cold Chassis. 25lbs. 




The Dumb Terminal for Smart People 

80X24 with full 128 char. ASCII UC+LC 
font with all control characters displayed. 
300-19,200 baud RS232. 2nd font addressable 
from keyboard in you-program-it 2708 for 
APL, Graphics sets, etc. Plug in monitor 
I/O connector, 110VAC and you are ready. 
INCLUDES: 'The Case', Cherry Kbd. A used 
monitor, ESAT 200A, all options except 
vector addressable cursor and modem. 
Bulletproof design and construction. 
Normally $675.00 What you always 
wanted your ADM3 to be: 

SYSTEM"A" $649.00 10/$5g9.00 



■PO Box 6721 Stanford! 




(.l^i 



THE FANTASTIC! 

MEMOREX FIVE-FIFTY 



S: 94305 

415-321-5601 
^ — »•» '< 

* Hard and Soft Sectoring 

* Single and Dual Density 
'Double side configuration 
as a retrofit at any time. 
*110l220V.50l60Hz 

*Pin for pin computable with 
Shugart 800,801,850,851 
(50 pin edge connector) 
$536,2/499, 5/475,10/449 
25/425, 100/405 
Double Sided Retrofit $200 





MINIDISKETTES (5.25') 1-9 10-24 25-H 
10, 16 or Soft Sector $4.79 4.65 4.45 

STANDARD (8') DISKETTES 
Hard or Soft Sector $5.99 5.33 4.79 



"The Case" Beautiful and sturdy 
anodized aluminum case in deep black designed to contain the 
ESAT 200A, and with a bezel cut out for the Cherry 'Pro' keyboard, 
(installed as shown above) Choose deep brown, light yellow, or crim- 
son to accent or color code your installation. The only choice for 
hard-use institutional and educational applications. $69.00, 10/ 59.00 



CASSETTES 
R-300 Certified Phillips Type $5.25 4.99 
1-150 Certified for audio decks $4.60 4.30 
('Kansas City' & SWTP formats) 



4.35 
3.90 



SURPLUS Muffin tvpe fans $7.95, Lambda Power Supplies 

5 V/70A.$ 145.00, 35A.$8'9.00, 16A-49.00, 1 2V/7.3A-S69.00 



OUR CATALOGUE 



Contains IC's, T.I. Sockets (1 cent/pin) 
Advice and much more. It is free. 



Ding and Handling: Surface: $o.40/ib. Air: $0:75/ib., 1.00 minimum 
Tax: 6.5% Insurance: $0.50 per $100.00 



Stand Alone ASCII Keyboard 








,«-. 



I f V f B j N 1 M 1 < I > 1 T "! .M.FT ^ lir 




■i34 SIMULTANEOUS OUTPUTS AVAILABLE: THE ONLY ONE 
ON THE MARKET 

1. SERIAL TTL LEVEL 

2. BUFFERED 8 BIT (TRI-STATE LATCH) PARALLEL 
OUTPUT WITH VALID DATA SYNC PULSE AND LEVEL 

3. 20 MA OPTO-ISOLATED CURRENT LOOP, POLARITY 
INDEPENDENT 

4. EIA RS232C 

liSINGLE +5 VOLT 300 MA (NOMINAL) POWER SUPPLY 

(REQUIRED) 
^INDUSTRY STANDARD 2 KEY ROLLOVER ENCODER 
li-ANSI-COMPATIBLE KEY SET; FOR SLIM-LINE "HIDE- 
AWAY" PACKAGING 

5 COMPONENT SALES INC. 
77B-A BRANMAN, SAN FRANCISCO. CA 3.41 03 
[41B] 861-134S 



oo 



ASSEMBLED 
AND TESTED 

Plus $3.00 handling charge. 
California residents 
add 6'/2% sales tax. 



^SEGMENTED SPACE BAR ALLOWS FAST MULTIPLE- 
SPACING WITHOUT REPEAT KEY 

irREPEAT KEY REPEATS AT CHARACTER RATE 

irUSER SELECTABLE UPPER CASE ONLY (KSR/ASR/33 
REPLACEMENT) OR UPPER/LOWER CASE 

liFACTORYSETAT 110 BAUD BUT EASILY ADJUSTED BY 
USER TO ANY BAUD RATE FROM 110 TO 9600 BAUD 

^FLEXIBLE PARITY 

*LED INDICATOR FOR SHIFT-LOCK KEY ELIMINATES 
CASE UNCERTAINTY 

*24 PIN DUAL-INLINE CONNECTOR 

6LOW PROFILE CASE (OPTIONAL) $40.00 

^Ml Orders accepted by phone or maU. ■■■■ 

MASTERCHARGE V VISA J COD* CHECK* MONEY ORDER 



Circle 60 on inquiry card. 



BYTE July 1978 183 



What's New? 



PERIPHERALS 



Centronics Announces Front Feed 
Option for 700 Series Printers 



Micromodule Has 16 Keys and 
IS Displays 




An optional front feed device has 
been Introduced by Centronics Data 
Computer Corp, Hudson NH 03051 . The 
front feed Is designed for use on eight 
members of the firm's 700 series of dot 
matrix printers and permits automatic 
front Insertion of cut forms and cut 
multipart form sets. It can be used In 
any application that requires informa- 
tion for Immediate utilization, Including 
invoicing, accounting, banlclngand stock 
certificates. The price for the front feed 
option is $700." 

Circle 639 on inquiry card. 



Assembled and Kit Plotters 




Plotter kits and plotters completely 
assembled are offered by Sylvanhllls 
Laboratory Inc, POB 646, Pittsburg KS 
66762. The kits require the purchaser to 
mount them on a drawing surface and to 
do the interconnection between the con- 
trol printed circuit boards and the com- 
puter. Plotters require an 8 bit parallel 
lO port and 5 and 24 V power sources. 
A basic 8080 software program Is In- 
cluded In the owner's manual. Applica- 
tions Include architectural, mechanical, 
and schematic drawings; printed circuit 
board artwork; positioning of small ob- 
jects; computer generated art; games; 
etc. Sizes available are 11 by 17 inches 
(30 by 43 cm) at $795 in kit form, 17 
by 22 Inches (43 by 56 cm) at $950 In 
kit form, and 22 by 34 Inches (56 by 86 
cm) at $1 300 In kit form." 

Circle 640 on inquiry card. 




■ B B B 

B B B B 

B B fl B 

B B B B 



This new Wince console lO module 
provides a versatile but inexpensive 
means of communication between a hu- 
man operator and a microprocessor. A 
16 key keyboard allows entry of parame- 
ters such as product codes, gas chro- 
matograph stream selects, etc, and 15 
7 segment displays. It allows output of 
data such as torque, item counts, etc. 
Also Included is a real time clock for 
providing Interrupts and displaying time. 
For further Information contact 
WIntek Corp, 902 N 9th St, Lafayette 
IN 47904.» 

Circle 641 on inqurry card. 




Add Some Color 



•*F 



«u 



The RM 9050 series, a new family of 
raster scan color Imaging and graphic 
systems, has been announced by the 
Ramtek Corp, 585 N Mary, Sunnyvale 
CA 94086. The RM 9150, 9250, 9350 
and 9351 are the first members of a 
compatible family of solid state digital 
television image generation systems capa- 
ble of displaying In color, gray scale and 
black and white. The series was devel- 
oped to provide a basic Imaging system 
plus graphics (plots, vectors and bar 
charts) and alphanumeric capability. 



The basic system Includes scrolling, 
character scaling, readback, cursor and 
interactive capabilities. An assortment 
of custom video boards are available 
providing enhancement lookup tables 
and digital to analog converters which 
can produce from 256 gray levels to 
4096 different colors. Keyboards and 
cursor controllers are available as add- 
on options. Pricing for a basic 64 color 
system is under $6000 with black and 
white less than $5500." 

Circle 642 on inquiry card 



Speed Up DECwrlters 




The SuperDEC throughput optimizer 
Is a printed circuit board designed to re- 
place the existing digital electronics In 
Digital Equipment's LA361 DECwrlter 
11 teleprinter, upgrading It to 1200 bps. 
Installation of the optimizer takes less 
than five minutes and Is completely plug 
compatible with the cables In the DEC- 
wrlter. Standard features Include auto- 
matic and manual top of form, full hori- 
zontal and vertical tabs (addressable and 
absolute), adjustable right and left mar- 



gins and an RS-232C Interface. Features 
not previously offered to DECwrlter 
users Include a double wide character 
set, bidirectional printing and 32 user 
programmable characters. An APL char- 
acter set, selective addressing and an 
answer back feature are optional. Price 
Is $395 with a one year warranty on all 
parts and workmanship. Contact Inter- 
tec, 19530 Club House Rd, Gaithers- 
burgMD 20760," 

Circle 643 on inquiry card. 



184 July 1978 ©BYTE Publicaiions Inc 



CaIIFoRnIa iNduSTRJAl 

Post Office Box 3097 B • Torrance, California 90503 



WORD PROCESSING PRINTER 



S255. 



IBM EXECUTIVE D" 



This Rubo Goldbergized printer, 
when properly interfaced to your 
data processing system, offers the 
capability of producing error free 
duplicate personalized letters. 
A seven bil TTL signal directs one 
of the 50 solenoid driven fingers to 
I depi'ess the proper typewriter key. 
Expandable incremental spacing 
allows the operator to software 
control justified copy. 
The heart of this machine is an 
Executive "D" serviceable by any 
IBM repair center. 
Shipping east of the Mississippi 
add $20,00; California add $10.00 
all other states add $15.00. 
(Copy above reduced to half size. ) 



CONNECTORS 



:r 



m 



your c.ioice 

DB25P 

male plug & hood 

or 

0B25S female 

^395 

Qty. fe. male hd. 
10 3.45 2.45 1.15 
25 3.15 2.25 1.05 
100 2.«5 1.90 .95 
500 2.25 1.50 .95 
IK 1 97 1.37 .73 



Edge 

Connectors 




100 PIN 

IMSAI/ALTAIR 



S-100 • GOLD PLATED • .125 "CENTERS 



AHair 140 row. solderlail. . 
imsai 250 row, sotdeflaiL . . 
3 Level Wire Wrap .250 row. 
SPECIALS 
W/W same as above without ear5$3.50 3/$10 
72 (dual 36) W/W 156" centers . $2.50 3/S6 



$5.98 3/$16.50 
$4.98 3/$11.95 
$4 98 3/$13.00 



S-100 Mother Board 
Quiet 




18 slot 
IMSA 



HEXADECIMAL KEYBOARD 

$34.95 



Maxl-Stivitcfi hexadecimal keyboards 

microcompuler syslems Ihat require ■ 

in standard hen code. 

Each assemtjiy consists of 16 hermati 

caliy sealed reed switches and TTL ' 

shot" debouncB circuitry 

Reliable low friction acelal resin 

piungefa are cfedded for the smooth 

operation and long life ot this premlu 

keyboard 

RoQui res single +5 volt supply. 




:fi ScptcH 




Diskettes 

8inchSoft<IBM) 
8 inch 32 sector 
Mini Soft sec. 
Mini 10 sector 
Mini 16 sector 



Certified Digital 

CASSETTES 



Won't drop a BIT! 



CALIFORNIA 
INDUSTRIAL 

is an 

Authorized 

Dealer ot 

Scotch Brand 

Data Products 




21i02 

LOW POWER 

450 nS 



7A% 

im 

7-1100 
7-1107 
74109 
74110 
74116 
74120 
74121 

n^^^ 

74123 
74125 
74126 
74128 
74132 
74136 
7414! 
74145 
4 47 




400 


3 


44 












44S 






7446 








7404 


19 






19 


7450 




.19 


7451 


7407 


25 


7453 




















7411 












7413 


49 




7414 


79 




7416 


39 




7417 


39 






















7425 


39 




7426 


.39 


7486 




















7430 


25 








7492 






7493 






7494 




39 


'495 


7440 


39 









301 H 


39 


350N 


« 






























304H ■ 


1^ 


370N 


y^ 






305H 


99 


373N 


119 






307H 


49 


377N 


199 






307CN 


39 


3eON 






.99 




99 
















CMOS 


309K 


99 


NE566 


1?9 










NE565H 


149 










NE565N 


1 /4 






311H 




NE566N 


1 i'S 


4007 


25 




99 






400B 


149 


312H 


199 


709H 


39 


4009 


69 


318H 


179 


709N 


;(q 


4010 


69 


318CN 


149 


710N 


/H 










711H 


w 






320K-5 -v 
3MK-12 > 






14 
























4015 


139 








149 


4016 


69 






733H 


149 


4017 


129 


320T-12 




733N 


99 


4018 


169 






739N 


1 14 










741 N 


IN 














4021 


149 










4022 


125 


340K-5 




746N 


;i9 


4023 


25 






1414N 


1/S 




1.19 


340K-12 




1458 


(j9 


S 


.25 






UART 




4028 


125 




















4030 
4032 


59 
49 


340T-12 ' 




•4.98 





SPECIAL 

GENERAL INSTRUMENT ASCII Keyboard Encoder 
AY 5-3600 Prime but house marked only $4.95 




TELETYPE MOraL 43 



New from Teletype, ihe Model 
43 Is capable of printing 132 ASCII 
characlera pe' line. Send and receive 
dataat I0of 30 char, persecond Key- 
board Qeneralea all 1 23 ASCII code combi 
tions RS-232 interface, same as the popui 
Model 33. Data sheet sen! upon request Manufac- 
turer suggested pr.ce It377 00. • ^ ** ^ *v 

IMMEDIATE DELIVERY >1219 

TTLmodel with NOVATIONbrand 
Acoustic Modem. n419 




TSP 






MAXI-SWITCH 

ASCII KEYBOARD 

Fully ftCS^.97 
Assembled •O^*.^' 



Definitely the best small systtmi keyboard that 
we have seen. Maxi-Switch has incorporated 
all the important keyboard features at a reason- 
able price. Full 128 ASCII funetions, "N" key 
rollover, automatic repeats, user designated 
special function keys, escape, control ^ lots 
of others. Data sheet upon request. 



FROM ATARI 

COLOR TELEVISION 
R.E MODULATOR 
1395 



HH 



mfinUfiL CRfiPHiTE 
DiSPLflV DEnERfiTDR 



Mprtetn teclinoiogy has P'Q 

Generator has the capaOilH) 
kwer case ASCII set Seii-cf 
the operator lo alimmalB e. 
Each umi is manutactureo ti 
QyGlanaaidssel'fiHlhCiy C£ 
every Ofder 



}r assembly allows 



JO 



Potter &Brumfield 
REED RELAY 

5voltcoil,pulls3.5v. 




.97 .79 .65 



Digital Casseite Drive 

COMPUTER CONTROLED 



•V9.50 




This precision I/O assembly features 
remote software controlled searchi 
capabilities. Two independent capstan 
drive motors allow the computer to 
control direction and speed of the 
transport. 

The assembly consists of a Raymoncl 
cassette transport, chassis, mother- 
board and three edge cards: read/write, 
capstan drive & control card. 
Current replacement valued at over 
$700.00. Schematics and complete 
documentation included. USED, but in 
excellent condition. 



SlOO PROTOTYPE BOARD] 

OPIOO-Moilmum design ver 
SQ'illtv along witti stondora 
oanress decoding and Dut 
tenng tor SlOO systems 
Room for 32 uncommiHeO 16 
pin ics. 5 bus buffer & de- 
coding cmps. 1 DIP address 
select swiicti o 5 volt regu 

WWIOO-Wire wrap breod- 
Doora, similar to the GPlOO 
Allows wire wrap of all sizes 
of sockets in any sizes of 
sooieis in any combinotion 
An extra reguloior position 
tor muiilDie volioge oopiico- 




TJujmbwheel 
switch 

Ten position 

BCD 

'139 «. 



r^ 



o;5eo 



Miniature / 
Switches A 



it 






$.69 

Conductor Fl. 

RIBBON WIRE 

TWISTED PAIR 



Transistors 

ea. 10 SO 100 



2N2222A.20 .li .16.15 
2N30S5 .69 .65 .59 .55 
.79 .75 .69 .65 
159 1(I9J391Z9 
.15 .11 .09.07 
.15 .11 .09.07 

odes 



Ml 3055 
2N3772 
2N3904 
2N3906 

Di 



10 a 100 
1N4002 100«. .08 06.05 
tN40a5 600>..10.08.07 
lN4148sitnal .07.05.04 
ittinb, red ea. 10 25 100 
LED'S h5.13.11.09 



Power Adapter 



6vdc,140mA 51.39 
7vdc, 1.4 A. 5.50 
9vdc. ISmA. 1.19 
10 vAc.300mA. 



■a 



Binding Posts 
5-WAY 



3.or*1.19 

20 100 
».35 .29 



SOLDERLESS 
TERMINAL^ 

INSULATED 
20lor 

♦.98 

Specify:22-18 16 14 

100 soo Ik 



.213. 679-9001 



RELAYS 

spot miniature 

10 25 100 
'l.l'ea $115 104 »9 

Coil 12 Volt dc. 
7 Amp Contacts 
P. C. Board Mount 



CAPACITORS 



ELECTROLrnCS 

«a. 10 50 



80,000/lOv. 355 3.M 2.95 
4500/50V.SW9 135 U9 

lOOO/lSv 555 49 45 
axial 



your choice 
t OO 1° 50 100 Ik 
*-9o s.gg .81.73.66 
SPDT Miniature Toggles 

7101 C&K ON'NONE-ON I 

7107 jM ON.OFF(mnt.ON) 

7108 CK ON-(moment.ON> I 

Rockec IBT . OPOI 

Rotary 3P-4-POS. 

Rotary 3P-6-POS. 

Pu&tiB<NO) S39ea4^$l 



.Idisc 
.01 disc 



512 .09 .07 
.06 .05 .04 



DIP Switch 



^Rfl 



$149 





Heavy 
dutf grounded 
power cord and mating 
chassis connectors. 



PANASONIC 

\9S 




"A A" 

450mA. 



DISCOUNT <| 

UJire UJfQp<entef 



IC SOCKETS 



pif 


Wire wrap 
ea. 25 50 


low profile 

ea. 25 SO 


8 




17' 16 IS 




14 


37<36 35 


18 17 16 


16 


38 37 36 


19 18 17 


24 


99 93 85 


36 35 34 


40 


169 155 139 


63 60 58 



saa.95 



50ft. 

'.98 



soo 1.000 11,000 
59. 515. $105. 



VISA 



Circle 39 on inquiry card. 



BYTE luly 1978 185 



Whal's New? 



PERIPHERALS 



Intelligent Parallel Printer Interface 
Card for Apple II Computer 




N 



Apple Computer Inc has introduced 
the Model A2B0002X intelligent printer 
interface card. The unit gives Apple II 
owners hard copy from popularly priced 
printers such as those offered by Axiom, 
Centronics, Qume, Printronics, OKI 
Data, SwTPC and other. Users can pro- 



duce permanent copy of program 
listings, generate reports, print letters 
and labels and generate graphics on 
printers with graphic capability. It comes 
fully assembled with instructions for 
connecting it to a printer. The card has 
a wide line format, capable of handling 
line widths up to 255 characters per line. 
It features high speed operation, up to 
5000 characters per second, the equi- 
valent of 3700 lines per minute at 80 
characters per line. The power require- 
ment is low, as card components are 
automatically powered down when no 
printing occurs and no external power 
is required for the card. It also features 
a general purpose 8 bit parallel output 
port. The card comes with firmware 
in read only memory, printer configur- 
ation block, ribbon cable and instruction 
manual. 

The price of the A2B0002X is $180. 
Contact Apple Computer Inc, 10260 
Bandley Dr, Cupertino CA 95014." 

Circle 619 on inquiry card. 



LSI-11 to Instrumentation Bus 




National Instruments, 8330 Burnet 
Rd, Austin TX 78758, has announced an 
interface from the Digital Equipment 



Corporation LSI-11 to the IEEE stand- 
ard 488-1975 general purpose interface 
bus (GPIB). The unit, designated the 
GPIB11V-1, can be used with either the 
LSI-11 or Heath H11. The unit is fur- 
nished with a 4 meter bus cable and a 
complete software package including 
drivers, utilities, and diagnostics. The 
drivers and utilities are furnished as 
MACRO source files which can be as- 
sembled as FORTRAN, BASIC or 
MACRO callable subroutines. The inter- 
face can be used with such GPIB devices 
as voltmeters, counters, frequency syn- 
thesizers, and other controllers such as 
the PET microcomputer. The unit, in- 
cluding software and cable, sells for 
$695." 

Circle 620 on inquiry card. 



New Improved TV Modification Kit 



TUM-41 
TU MOD KIT 



The TVM-04 television modification 
kit (see May 1978 BYTE, page 22) has 



been superseded by the improved 
TVM-41, allowing greater monitor band- 
width than with the TVM-04. The new 
80 character video generator displays 
look crisp and sharp. Operation as a 
monitor or TV receiver is switch select- 
able. The TVM-41 also extends the num- 
ber of sets which can be modified to in- 
clude Hitachi model number P-04, P-05, 
P-08, PA-4, PA-5, PA-8, P-40, P-41, 
(all 12 inch) and the 9 inch model 1-28. 
Total cost for the monitor is about 
$100, depending on the local price of 
the TV set. The TVM-41 is priced at $20 
including hardware, wire and a five foot 
video cable for connecting to your video 
source. For more information contact 
Pickles & Trout, POB 1205, Goleta CA 
93017." 

Circle 621 on inquiry card. 



"OEM 11" Brochure on Open Frame 
DC Power Supplies 

A new 12 page, illustrated brochure 
is now being offered by Powertec Inc, 
9168 DeSotoAv, Chatsworth CA91311 
that describes the company's OEM II 
series of second generation, open frame 
DC power supplies. Described in the bro- 
chure are Powertec's broad product 
range of single output low power to 375 
W, and multiple outputs dual and 
triple power supplies. The printed cir- 
cuit board electronics have been de- 
signed to provide high efficiency and 
low primary power consumption. A list- 
ing of specifications is also included. 
Voltage and current rating charts are 
listed for user convenience." 

Circle 622 on inquiry card. 



Glitch Exterminator for the 
S-IOOBus 




Vamp Inc has introduced the Ex- 
terminator (VTE-100) which they claim 
puts an end to bus problems on S-100 
computer systems. The VTE-100 is a 
dual function board serving as a bus 
terminator and card extender. Bus 
termination by the VTE-100 is said to 
clean up noise, cross talk, overshoot and 
other bus problems that can scramble 
data unpredictably. The board also 
serves as a card extender for memory or 
lO cards which may require analysis or 
maintenance. The Exterminator, through 
on board termination, eliminates inter- 
ference from adjacent boards which may 
radiate digital RF allowing any memory 
or lO card to be extended without fear 
of having the board perform unpredict- 
ably. It fuses all extended power buses 
to protect both the extended card and 
the power supply from any accidental 
damage. The fuses also allow for easy 
access to all power buses to permit the 
monitoring of current consumption. The 
Exterminator comes fully assembled and 
tested for $49.95 plus $2 to cover ship- 
ping and handling from Vamp Inc, POB 
29315, Los Angeles CA 90029." 

Circle 623 on inquiry card. 



186 



luly 1978 ©BYTE Publicjtiom Inc 



• • •••' 

m, m • • • • 

• •• • • • ? ? 






•••••••••••••••••••••••••••••••••••••I 



•••• 

••••• 
••••• 
••••• 
••••• 
••••• 



I***- 
■••••■ 



I***- 









•••••' 



^l 



KIT FEATURES: 



16K E-PROM CARD 

IMAGINE HAVING 16K OF SOFTWARE ON LINE AT ALL TIME! 
S-100 [Imsai/AltaJr] Buss Compatlile! 



••.-.••••A 



1. Double sided PC board with solder 
mask and silk screen and gold plated 
contact fingers. 

2. Selectable wait states. 

3. All address lines & data lines buf- 
fered! 

4. All sockets included. 

5. On card regulators. 

KIT INCLUDES ALL PARTS AND 
SOCKETS (except 2708's). Add $25. for 
assembled and tested. 




PRICE CUT! 






$57.50 kit 



SFtCUL OFFED: 



WAS $69.95 



DEALER INQUIRIES INVITED! 



Our 27a8's (ABONS) are 
when purchased with above kit. 



$12.95 



■i<M 



Swli^ 



KIT FEAUKS: 



ADD 

$20 FOR 

250 NS 



1. Doubled sided PC Board with solder 
mask and sijk screen lavout. Gold 



plated contact fingers. 



ill sockets included. 
Fully buffered on 
data lines. 

Phantom is jumper 
pin 67. 
FOUR 
on card 



all address and 
selectable 



7805 



regulators are provided 
(ASONS) 



8K LOW POWER RAM KIT-$149.00 



S-100 (Imsai/Altair) Buss Compatible! 2 kits for $279 

Fully Assembled & Burned In 

$179.00 

Blank PC Board w/ Documentation 

$29.95 

Low Profile Socket Set 13.50 

Support IC's (TTL & Regulators) 

$9.75 

Bypass CAP'S (Disc & Tantalums) 

$4.50 




USES 21 L02 RAM'S! 



MOTOROLA QUAD OP ■ AMP 

MC3401, PIN FOR PIN SUB. 
FOR POPULAR LM 3900, 



3 FOR $1 



ALARM CLOCK CHIP 

N S MM5375AA Six Digits 
With full Data New! 

$1 .95 each 



MOTOROLA 7805R VOLTAGE REGULATOR 

Same as standard 7805 except 750 MA output. 
TO-220. 5VDC output. 

44c each or 10 for $3.95 



FULL WAVE BRIDGE 

4 AMP. 200 PIV. 
69e 10 FOR $5.75 



NOT ASSOCIATED WITH DIGITAL 
RESEARCH OF CALIFORNIA. THE 
SUPPLIERS OF CPM SOFTWARE. 



450 NS! 2708 EPROMS 

Now full speed! Prime new units from a major U.S. Mfg. 450 N.S. 
Access time. 1 K x 8. Equiv. to 4-1 702 A's in one package. 



$15.75 ea. 



4 FOR $50 



00 



OUR LATEST COMPUTER KIT! 



WHY THE 2114 RAM CHIP? 

We feel the 21 14 will be the next industry 
standard RAM chip (like the 2102 was). 
This means price, availability, and 
quality will all be good! Next, the 2114 is 
FULLY STATIC! We feel this is the ONLY 
way to go on the S-100 Buss! We've all 
heard the HORROR stories about some 
Dynamic Ram Boards having trouble 
with DIVIA and FLOPPY DISC DRIVES 
Who needs these kinds of problems'' 
And finally, even among other 4K Static 
RAIVI's the 2114 stands out! Not all 4K 
static Rams are created equal! Some of 
the other 4K's have clocked chip enable 
lines and various timing windows just as 
critical as Dynamic RAM's. Some of our 
competitor's 16K boards use these 
"tricky" devices. But not us! The 21 14 is 
the ONLY logical choice for a trouble- 
free, straightforward design. 



FULLY S-100 COMPATIBLE! FULLY STATIC, AT DYNAMIC PRICES! 

16K STATIC RAM KIT, ^ _^ 

separate 4K 






sasgoo 

COMPLETE KIT 



four 



^ 



SPECIAL 

INTRODUCTORY OFFER! 

Buy 2 KITS (32K) for $650 

450 NS 



Blank PC Board with Documentation 

$33.00 

LOW PROFILE SOCKET SET- $12.00 

ASSEMBLED & TESTED - ADD $30.00 

2114's 4K RAM's - 8 for $85.00 



KIT FEATURES: 

1. Addressable as 
Blocks. 

2. ON BOARD BANK SELECT circuitry. 
(Cromemco Standard!) Allows up to 
512K on line! 

3. Uses 2114 (450NS) 4K Static Rams. 
4 ON BOARD SELECTABLE WAIT 
STATES. 

5. Double sided PC Board, with solder 
mask and silk screened layout. Gold 
plated contact fingers. 

6. All address and data lines fully 
buffered. 

7. Kit includes ALL parts and sockets. 

8. PHANTOM is jumpered to PIN 67. 

9. LOW POWER: under 2 amps TYPICAL 
from the +8 Volt Buss. 

10 Blank PC Board can be populated as 
any multiple of 4K 



Z-80 PROGRAMMING MANUAL 

By Mostek. The major Z-80 second 
source. The most detailed explanation 
ever on the working of the Z-80 CPU 
CHIPS, At least one full page on each of 
the 158 Z-80 instructions. A MUST 
reference manual for any userof theZ-80. 
300 pages. Just off the press. 
$12.95 



HEAVY DUTY! 

Full Wave Bridge 
25AMP 50PIV 

$1.25 



Tarttalum Capacitors 

1 MFD. .35V. By 
Kemet. Axial Lead. 
Best Value! 10/$1. 



GE 10 AMP Triac 

SC146D. House no. 

To-220 case. Rated 

10amps400PIV. 

75c ea. 3/$2. 



Digital Research Corporation 

** (OF TEXAS! ■ 

P. O. BOX 401247 • GARLAND. TEXAS 75040 • (214) 271-2461 



New! REAL TIME 

Computer Clock Chip 

N.S, MM531 3. Features 
BOTH 7 segment and 
BCD outputs. 28 Pin 
DIP $4.95 with Data 



LSSER 

74LS00 — 33c 
74LS02 — 35c 
74LS04— 35c 
74LS08 — 35c 
74LS10— 33c 
74LS20 ~ 33c 
74LS73 — 49c 



lESTTL 

74LS74 — 49c 
74LS90 —69c 
74LS138— 89c 
74LS154— 1.49 
74LS175— 1.10 
74LS367— 75c 
74LS368— 85c 



TERMS: Orders under SI 5. add 75c. No COD's. We 
accept VISA, MasterCharge and American Express 
Cards. Money Back Guarantee on all items! Texas 
Residents add 5% Sales Tax. WE PAY POSTAGE! 



•••:.:•. • 



»••••••••« 



••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••J 



Circle 100 on inquiry card. 



BYTE July 1978 187 



Circle 297 on inquiry card. 



^ YOUR BEST BUY IN WIRE WRAP SUPPLIES ^ 



PRECUT WIRE 

WHY BUY WIRE ON ROLLS' 
PRECUT a STRIPPED WIRE IS: 

• Fail - No more Cutting & stripping by hand 

• R*Habl« - Good, clean, uniform strip 

• Economical - Cheaper than using bulk wire 





Pracul Wirt 




Bulk WIra 


100 0C3 

100 PCS 

WireK 


oi 3 at S 82 ^ 3-'<c/ti. 
ol 6' at 1 06 ae/tt- 
1 at (6 95 = 2 1/»/n. 


so It roll at 
00 It foilai 


1 99 ^ 4«/ft. 

2 95 - 3C/ft. 


« SOKynarsliippad 1 c 
Colors fled. Blue, Green 
Wire packaged m ptasti 


n eacr> end Lengths are ovetaM 
Veiiow. Black. Orange. While 
Dags Add 25«'length for tubes 


2'', in 
3 in 
3'^ in 


100 

78 
82 
86 
90 


500 

2 40 
260 
280 
300 


1000 

4 30/K 

4 7t/K 
S12/K 

5 52/K 


5SS0 

3e9^K 
4 22/K 

4 55/K 
4 8e'K 


4* in 

5 in 
5'^ in 

6 in 


94 
96 

1 02 
1 06 


3 21 
3 42 
3 65 
3S5 


5 93/K 

6 34/K 

6 75/K 

7 16/K 


5 21/K 
5 52/K 

5 86/K 

6 19/K 


6'^in 

7-, in 
8 in 


1 15 
1 20 
125 

129 


4 05 
4 25 
4 45 
4 65 


7 57-'K 

7 98/K 

8 39/K 
BaO'K 


6 52/K 

6 85/K 

7 18/K 
7 53/K 


8>j in 

9 in 
gwin 

10 in 


1 32 
136 
1 40 
1 45 


4 85 

505 

5 25 

5 51 


9 2t/K 
9 62'K 
10 03/K 

10 44/K 


7 84/K 
ei7/K 

8 50/K 
8 83/K 


Addi 


nches iO 


41 


82/K 


66/ K 




WIRE KITS 




£J 


$6.95 




= 2 ?19.W 



250 
250 
100 


3- 100 *r 250 2'V 

3V 100 5' 500 3- 

4" 100 6" 500 3'->' 

500 4 

Choote Or>e Color 
or Assonmeni 


250 4',. 

250 5' 

100 5/ 

1 250 


250 6- 

100 6 -■ 
100 7 
Hon Bulk 



WIRE WRAP SOCKETS 



10-24 25-99 100-249 250-999 1K-5K 



18pin- 
?0p.r. 
22 pin ■ 
24 pin 
28 pin 
40 pin 



Gold 3-lev*l CloMd Enlry Sockelt 
d & Side SlBCkaDle All pncM include gold 

Tin sockeli and 2-ievei sockets available 



^ INTERCONNECT CABLES^ 



bon caDle conneclors 'or connecUng 
Ironl panels, or board to board 


Boards lo 


SINGLE ENDED 


DOUBLE ENDED 


I4p,n 16 pin 


24p>n 


14 pm 


16 pin 24 pm 


124 1 34 
1 33 1 44 
152 165 
1 91 2 06 


205 

2 24 
263 

3 40 


2 24 
2 33 
2 52 
291 


2 45 3 37 
2 55 3 92 
2 76 4 31 
317 508 



WIRE WRAP TOOLS 




$34.95 

With Free Wire Kit 
(S6 95 Value) 
HOBBY WRAP 
Model BW 630 



Batteries & Charger $11.00 

WSU 30 Hand Wrap-Unwrap Strip Tool 5 95 

WSU 30M, for Modified Wrap 6 95 

BT 30 Extra Bit 2,95 







WIRE WRAP BOARDS 














14 


5J 


WW 
1024 Connector 


H-PCB 1 

3662 

3682 


4x4'.', 

4x6 

4x10 


44 
44 
44 


Buses on both sides 

Blank 

Buses on one side 


4 76 
625 
10,50 


4 50 
6,85 
10,00 


4 00 
5,50 
9,50 


3,00 
3,00 
300 


36822 
4066-4 
3719-1 


4x6 
4x6 
4x6 


44 
72 
72 


Buses on one side 
Buses on bolh sides 
Blank 


950 
13 60 
900 


900 
13,00 
8,50 


825 
12,50 
800 


3 00 

4 00 
4 00 


3719-4 

4350 

8800V 


4x10 
7.9'', 
10x5.3 


72 
80 
100 


Blank 

Buses on both sides 

Buses on bolh sides 


11.00 
17 50 
19,50 


1050 
16,50 
17,96 


10,00 
16 00 
16 96 


4 00 
700 
500 


169P84 


8v,x 1 7 




Blank 


626 


5.75 


5,26 


- 


SOCKET 
SAI ^' 


14 p 
16 p 

24 p 


n Gold WVW Socket 
n Gold WW Socket 
n Gold WW Socket 




30 

,32 
,75 


27 pe 
,29 pe 
,65 pa 


400 
350 

117 






44 p 


n ST Edge Cerd Cddnector 


1.75 


1 50pe 


10 



100 pin ST Edge Card Connecior 3. SO 3.00 par 10 

lOOpin WW Edge Card Connector 3.50 3,00 par 10 

Prices good through 8/1/78 vvhen purchased with Wire Kit —1 or -2 

PAGE DIGITAL 
ELECTRONICS 

Ordering Information: 

Orders under S2S and COD'S, add $2 

All others, shipped ppd m US via UPS 135 E. Chestnut Street 5 

For Blue Label (Air) or 1st Class, add $1 Alt^^w^nln r^nlif^^^',.^ omic 

weacceptv,Mj,Mas«rch.rg, Monrovia, California 91016 

Most orders shipped same day 

Dealer Inquiries Invited 



Phone (213) 357-5005 




P.O. Box 4430X Santa Clara. CA 95054 
For will call only: (408) 988-1640 



^^^^For will call only: (408) 988-1640 
^^^^^^2322 Walsh Ave.^ 

^^B^^ ELECTRONICS 

"^^^ CRYSTALS 













1 MHz 4.50 2.0100 MHz 


1,95 












2 MHz 4.50 2.097152 MHz 4.50 


MICROPROCESSOR 


2708 14.65 


2104A-4 


4.95 


4 MHz 4.25 2.4576 MHz 


4.50 


6800 


19.50 


DH8577 290 


2107B 


4 95 


5 MHz 4.25 3.2766 MHz 


4,50 




8.95 


8223 290 


2111-1 


4 95 


10 MHz 4,25 5,0688 MHz 


4.50 


m 


29.95 


2716 28,95 


2112-2 


3.95 


18 MHz 3.90 5.185 MHz 


450 


8212 






2114 


8.50 


20 MHz 3.90 5.7143 MHz 


4.50 


8214 


8.00 


IC SOCKETS 


MK4116 


27 50 


32 MHz 3.90 6.5536 MHz 


4.50 


8216 


2.90 




2513B 


6.30 


32768 Hz 4.00 14.31818 MHz 4 25 


8224 


2,95 


PIN 1 UP PIN lUP 


21L02-1 


1.49 




4.50 


8228 


5.35 




MM5262 


.40 


3.5795 MHzl. 20 22 1164 MHz 4,50 


8251 


9.25 


14 ,18 28 .42 


MM5280 


3.00 


60 Hz Cryital Time Bate Ktl 


S 4.40 


8253 


10.00 


16 -20 36 .58 


MM5320 


9,95 


30 MHz Fffiquencv Counter Kit 


S47.7S 






18 .27 40 .61 






PrHCslv Kit to 350 MHz 


$19.95 


CDP1802CD 


19.95 


22 30 


PD4110-3 


4.00 






CDP1802D 


25,00 




PD411D-4 


5.00 






CDP1861 


12.96 




P5101 


13.95 






6620 






4200A 


12.95 






6850 


12 95 




82S25 


290 
















Extender .Board w/connectot 














Video Interlace board kit 


125.00 


PROM 










16K EPROM board kit w/o PROMS 74 50 




3.95 








16K Static RAM board kit 


395 00 


N82S23 


2,95 








North Stir Hoppy Dlik Kit 


>665 00 


N82S123 


3.50 








Additional Drive Kit 




N82S126 


3-75 


MOSMEMONT RAM 


INTERFACE 




Parstrofllct IMA Logic 




















8.75 


2102AL-4 1,60 


8T28 


2.75 


Model 10 Trigger Expandef Kit 




^8^s^37 


8.75 


21F02 1-85 


8T97 


1.69 


Model 150 Bus Grabber Kit 


S369.00 



New Cosmac Super "ELF" 

RCA CMOS expandable to 64K microcomputer 
w/H EX lieypad input and video output for graphics. 
Just turn on and start loading your program using 
the resident monitor on ROM. Pushbutton selec- 
tion of all four CPU modes. LED indicators of 
current CPU mode and four CPU states. Single 
step op. for program debug. Built in pwr. supply. 



256 Bytes of RAM, audio amp. & spkr. Detailed 
assy. man. w/PC board & all parts fully socketed. 
Comp. Kit $106.95. High address display option 
8.95; Low address display option 9.95; Custom 
hardwood cab.; drilled front panel 19.75; Nicad 
Battery Backup Kit w/all parts 4.95; Fully wireij S, 
tested in cabinet 151.70; 1802 software club. 
10-12 pg. monthly publication 12.00 per yr. 



Auto Clock Kit $15.95 

DC clock with 4. 50' displays Uses National 
MA-1012 module with alarm option. Includes 
light dimmer, crystal timebase PC boards. 
Fully regulated, comp. instructs. Add S3. 95 
for beautiful dark gray case. Best value any- 
where. 



4K Ell Expansion Board Kit with Cassette l/F $79.95 

Available on board options; 1 K super ROM monitor S19.95. Parallel I/O port $7.95. RS232 l/F $3.50. 
TTY 20 ma l/F $1.95. S-100 Memory l/F $4.50. 

Tiny Basic for ANY 1802 System 

"oltZ Monitor mil ^'"^ E" ™"«'= «*» 30%off. 



Object code listing or 
paper tape with manual 



$5.50 



78 IC Update Master Manual 

1978 IC Update Master Manual $30.00 

Complete IC data selector 2175 pg. Master ref- 
erence guide. Over 42.000 cross references. 
Free update service through 1978. Domestic 
postage $3.50, Foreign $6,00. Final 1977 
Master closeout $15.00 



Video Modulator Kit $8.95 

Convert your TV set Into a high quality monitor 
without affecting normal usage. Complete kit 
with full Instructions. 



RCA CosmacVIP Kit $275.00 

Video computer with games and graphics. 



Sinclair 3V2 Digit Multimeter 

Batt. oper. ImV and 1NA resolution. Resis- 
tance to 20 meg. 1% accuracy. Small, portable, 
completely assem. in case. 1 yr. guarantee. 
$50.05 



FREE; Send for your copy of our NEW 1978 QUEST CATALOG. 



lericard and 
e 24« stamp 



188 BYTE luly 1978 



Circle 307 on inquiry card. 



ELECTRONIC SYSTEMS 

Dept. B P.O. Box 21638 San Jose, CA 95151 

FOR CATALOG INCLUDING PARTS LISTS AND SCHEMATICS. 
SEND A SELF ADDRESSED ENVELOPE WITH 2i«r POSTAGE. 



RS-232/TTL 
INTERFACE* 




UART 
&BAUD 
RATE 
GENERATOR* 

Part no. 101 

• Converts serial to parallel and 

parallel to serial 

• Low cost on board baud rate 
generator 

• Baud rates: 110, 150, 
300,600, 1200, and 2400 

• Low power drain +5 volts and 
- 1 2 volts required 

• TTL compatible 

• All characters contain a start 
bit, 5 to 8 data bits, 1 or 2 stop 
bits, and either odd or even 
parity. 

• All connections go to a 44 pin 
gold plated edge connector 

• Board only $12.00; with parts 
$35.00 



8K 

STATIC 

RAM 




Part no. 300 

• 8K Altair bus memory 

• Uses 2102 Static memory chips 

• Memory protect 

• Cold contacts 

• Wait states 

• On board regulator 

• S-100 bus compatible 

• Vector input option 

• TRl state buffered 

• Board only $22.50; with parts 
$160.00 




, and 



Part no. 232 

• Converts TTL to RS-232, 
converts RS-232 to TTL 

• Two separate circuits 

• Requires 12 and +12 volts 

• All connections go to a 10 pin 
gold plated edge connector 

• Board only $4.50; with parts 
$7.00 




DC 

POWER 

SUPPLY* 



Part no. 6085 

• Board supplies a regulated 
-^5 volts at 3 amps., + 12, - 12, 
and -5 volts at 1 amp. 

• Power required is 8 volts 
AC at 3 amps., and 24 volts AC 
C.T. at 1.5 amps. 

• Board only $ 12.50; with 
parts S42.50 excluding 
transformers 



TIDMA' 



Part no. 112 a^'^f 

• Tape Interface Direct Memory 
Access 

• Record and play programs with- 
out bootstrap loader (no prom) 
has FSK encoder/decoder for 
direct connections to low cost 
recorder at 1200 baud rate, and 
direct connections for inputs and 
outputs to a digital recorder at 
any baud rale. 

• S-100 bus compatible 

• Board only $35.00; 
with parts $110.00 




Part no. Ill 

TAPE 
INTERFACE* 

• Play and record Kansas City 
Standard tapes 

• Converts a low cost tape 
recorder to a digital recorder 

• Works up to 1200 baud 

• Digital in and out are TTL-serial 

• Output of board connects to 
mic. in of recorder 

• I^phone of recorder connects 
to input on board 

• Requires -^5 volts, low power 
drain 

• Board $7.60; with parts $27.50 

• No coils 




Part 
no. 107 

RF 
MODULATOR* 

• Converts video to AM modu- 
lated RF, Channels 2 or 3 

• Power required is 1 2 volts AC 
C.T., or +5 volts DC 

• Board $7.60; with parts $13.50 




Apple II 
Serial I/O 
Interface * 

Part No. 2 

• Baud rates up to 30,000 

• Plugs into Apple Peripheral 
connector 

• Low-current drain 

• RS-232 Input and Output 

SOFTWARE 

• Input and Output routine from 
monitor or BASIC to teletype or 
other serial printer. 

• Program for using an Apple II 
for a video or an intelligent ter- 
minal. Board only — $15.00; 
with parts — $42.00; assembled 
and tested - $62.00. 



RS-Z32/TTY* 
INTERFACE ^ 

Part no. 600 J^^ 

• Converts RS-232 to 20mA ^^ 
current loop, and 20mA current 
loop to RS-232 

• Two separate circuits 

• Requires +12 and -12 volts 

• Board only S4.50, with 
parts «7.00 



TELEVISION 
TYPEWRITER 




Pari no. 106 

• Stand alone TVT 

• 32 char/line, 16 lines modifi 
cations for 64 char/line included 

• Parallel ASCII (TTL) input 

• Video output 

• IK on board memory 

• Output for computer con- 
trolled curser 

• Auto scroll 

• Non-destructive curser 

• Curser inputs: up, down, left, 
right, home. EOL, EOS 

• Scroll up, down 

• Requires +5 volts at 1.5 amps, 
and - 12 volts at 30 mA 

• All 7400, TTL chips 

• Char. gen. 2513 

• Upper case only 

• Board only 839.00; with parts 
8145.00 



MODEM 




Part no. 109 

• Type 103 

• Full or half duplex 

• Works up to 300 baud 

• Originate or Answer 

• No coils, only low cost com- 
ponents 

• TTL input and output-serial 

• Connect 8 ohm speaker and 
crystal mic. directly to board 

• Uses XR FSK demodulator 

• Requires +5 volts 

• Board $7.60; with parts $27.50 



To Order: 



Mention part number and description. For parts kits add "A" to part number. Shipping paid for orders 
accompanied by check, money order, or Master Qiarge, BankAmericard, or VISA number, expiration 
date and signature. Shipping charges added to C.O.D. orders. California residents add 6.5% for tax. 
Parts kits include sockets for all ICs, components, and circuit board. Documentation is included with 
all products. Dealer inquiries invited. 24 Hour Order Line: (408) 226-4064.* Designed by John Bell. 



Circle 125 on inquiry card. 



BYTE )ulv 1978 189 



What's New? 



PERIPHERALS 



Isolated Digital Output Board 
for Intel Microcomputers 



A Video Camera Kit 




This 202 video camera kit may be 
used for visible or infrared viewing and 
surveillance with an infrared light source, 
and is excellent for standard surveillance 
work because of its light weight (under 
one pound) and small size {VA by 6V2 
inch boards). A 5 V, 1 A power supply is 
needed. The kit includes all semicon- 
ductors, boards, data sheets, diagrams, 
resistors, capacitors, and an 8 mm lens. 
The kit sells for $349 from Solid State 
Sales, POB 748, Somerville, MA 021 43.- 

Circle 61 5 on inquiry card. 

Video Terminal Offered by Phone 1 




The new model PI -11 video terminal 
features the following: 80 by 24 screen, 
local editing, upper and lower case dis- 
play, dual screen intensity, full or half 
duplex operation, numeric cluster key- 
board, and 300 bps acoustical modem. 
The unit sells for $1075 complete and 
$800 for the terminal alone. Contact 
Phone 1 Inc, 1330 E State St, Rockford 
IL61108.- 

Circle 616 on inquiry card. 



Module Interfaces Voice and 
Instruments to Synthesizers 



PITCH 
FOtLOWER 







The Aries AR-333 pitch and envelope 
follower is an electronic module that in- 
terfaces external signal sources, such as 
voice, single note instruments, and tape 
recorders, to most synthesizers. A one 
octave change of input signal produces a 
1 V change in pitch control output for 
controlling VC oscillator frequency, fil- 
ter frequency, etc. Linear and logarith- 
mic envelope follower outputs allow 
control of synthesizer functions by the 
amplitude of the input signal. On the 
front panel, a trim pot lets you adjust 
the tracking sensitivity of the pitch con- 
trol output, and permits use of the mod- 
ule with different synthesizers without 
retrimming oscillators. The front panel 
also provides a tuning control for adjust- 
ing oscillator frequency which allows 
tuning to the pitch of other instruments, 
and a retriggering sensitivity control for 
picking up accents. A low distortion 
compressor output is also provided. The 
module's 36 db, low noise microphone 
preamp accepts Vi inch phone plugs. It 
sells for $349 (kit) and $499 (assem- 
bled). An assembled AR-333 with case 
and power supply (Model GE-101) sells 
for $550. Contact Aries Music Inc, Shet- 
land Industrial Park, POB 3065, Salem 
MA 01970." 

Circle 61 8 on inquiry card. 




Plug compatible 16 or 32 channel iso- 
lated digital output systems are available 
for the Intel SBC 80 and Intellec MDS 
microcomputers. Isolation eliminates 
ground loop problems and protects the 
processor from real world transients. 
Memory mapped MP801 (16 channel) or 
MP802 (32 channel) systems are con- 
tained on a single printed circuit board 
and provide all control and timing 
circuitry. Channels are implemented by 
dry reed relays protected by metal oxide 
varistors and can handle up to 10 W. Re- 
lays provide low "on-impedance," high 
output current and isolate output chan- 
nels from the computer bus (to 600 
VDC) and from channel to channel 
(300 VDC). They are treated as memory 
by the processor, eight output channels 
occupying one memory location. Prices 
of the 16 channel MP801 are $295 and 
$475 for the 32 channel MP802 in quan- 
tities of one to nine. Contact Burr- 
Brown, International Airport Industrial 
Park, Tucson AZ 85734.» 

Circle 61 7 on inquiry card. 



Attention Readers, and 
Vendors. . . 

Where Do New Product Items 
Come From? 

77!e information printed in tlie 
new products pages of BYTE is 
obtained from "new product" or 
"press release" copy sent by the 
promoters of new products. If in 
our Judgment the neat new whiz- 
bang gizmo or save the world 
software package is of interest 
to the personal computing experi- 
menters and homebrewers who 
read BYTE, we print the informa- 
tion in some form. We openly 
solicit such information from 
manufacturers and suppliers to 
this marketplace. The information 
is printed more or less as a first in 
first out queue, subject to oc- 
casional priority modifications. 



190 



luly 1978 ©BYTE Publicjtions Inc 



c^^ri.1 T-W7 n/./^n A "Smart" VIDEO BOARD 
^^^^ Ihe tW-2001 KIT At A "Dumb" Price! 

'^ A VIDEO BOARD + A MEMORY BOARD + AN I/O BOARD - ALL IN ONE! 

■ STATE OF THE ART TECHNOLOGY USING DEDICATED MICROPROCESSOR I.C. 4^ 1 QQ O ^ 

■ NUMBER OF I.C.s REDUCED BY 50% FOR HIGHER RELIABILITY ■ MASTER PIECE ^fl? J- 3/ 3/« 37 tJ 

OF ENGINEERING ■ FULLY SOFTWARE CONTROLLED Priced at ONLY Basic Software Included 

SPECIAL FEATURES: ■ Programmable no. of scan lines OPTIONS: 

■ S-100 bus compatible ■ Underline blinking cursor Sockets SI 0.00 

■ Parallel keyboard port ■ Cursor controls: up, down, left, 2K Static Memory 

■ On board 4K screen memory right, home, carriage return (with Sockets) $45.00 

(optional)* relocatable to main ■ Composite video 4K Static Memory 

computer memory *Min. 2k required for operation of this board. (with Sockets) S90.00 

■ Text editing capabilities (soft- DISPLAY FEATURES- Complete unit, assembled 
ware optional) _ .^^ ,. , ., .g^„ . ^ and tested with ' 

■ Scrolling- UD and down through " 128 displayable ASCII charact- 4K Memory S335.00 

icroumg. up dnu uown uiruugn ers (upper and lower case alpha- „ . , „^.. „^^ ^^ 

video memory numeric, controls) Basic software on ROM . S20.00 

■ Bhnking characters a 64 ^j. 32 characters per hne Text editor on ROM .... S75.00 

■ Reversed video Oumper selectable) 

■ Provision for on board ROM ■ 32 or 16 lines 

■ CRT and video controls fully Oumper selectable) 

programmable (European TV) ■ Screen capacity 2048 or 512 DEALER 

' ?rn dot^maTrlx""' INQUIRIES WELCOMED 



8080 SUPPORT 

8212 S3.00 

8214 7.95 

8216 3.50 

8228 5.95 

8251 7.95 

8555 8.50 

1/4W RESISTOR 

10 Ohm- 1.5m 

$1.75/100 

of one value 



Pole lOPos. 
ROTARY 
SWITCH 

3 for $1.00 



Pole 8 Pos. 
T05 Miniature 
Rotary Switch 
3 for $1.00 



MINIATURE 

Slide Switch 

DPDT 

$.15: 10/$1.00 



Push Button 
Momentary 

Switch 
3 for $ 1 .00 



a 



080 A 



CPU 

$7.75 



RAM-2II4 

lKx4 450ns 
$8.00 



RIBBON CABLE 

32 Conductor 

26 AWG - $.60/Foot 



HEXADECIMAL 
LABEL KEYBOARD 

Matrix coded output 

Interfaces with 74C922 

for binary code 

Zero bounce 

Est. life: 100 million 

Remove back to stick on 



SHIPPING: Keyboard and Video Board: $3.50; others: $1.25 
California residents add 6% sales tax 



ELECTRONICS WAREHOUSE Inc. 

1603 AVIATION BLVD. 
REDONDO BEACH, CA. 90278 

TEL. (213)376-8005 
WRITE FOR FREE CATALOG 

Minimum Order: $10 




•JfONLY 



ASCII 3rd GENERATION 

KEYBOARD KIT *68.00 




TTL Logic Circuits 

Power: +5V 275mA 

Upper and Lower Case 

Full ASCII Set (Alpha 
Numeric, Symbols, 
Control) 

7 or 8 Bits Parallel Data 

Optional Serial Output 

Selectable Positive or 
Negative Strobe, and 
Strobe Pulse Width 

'N' Key Roll-Over 

Fully Debounced 

Carriage Return Key 

Repeat Function Key 

Shift Lock, 2 Shift Keys 

4 User Defineable Keys 

P.C. Board Size: 

17-3/16" x 5" 



OPTIONS: 



Metal hnclosure 
Painted IBM Blue 
and White) 


$25.00 


18 Pin Edge Con. 


S2.00 


I.C. Sockets 


$4.00 


Serial Output (Shift 
Register) 


$2.00 


Upper Case Lock 
Switch for Capital 
Letters and 
Numbers 


$2.00 



KIT INCLUDES: Keyboard, 
P.C. Board, all required com- 
ponents & assembly manual. 

NOTE: If you have this 63 
Key Teletype Keyboard you 
can buy the Kit without it 
for only $44.95. 



Circle 130 on inquiry card. 



BYTE July 1978 



191 



What's New? 



Full Character Line Printer 



PERIPHERALS 



The Writehander: a New Typing 
Keyboard for One Hand 




A typing keyboard has been designed 
that permits typing all 128 characters 
of the ASCII code with one hand and is 
particularly useful with computers and 
terminals that accept ASCII coded 
parallel input. To use the Writehander, 
the typist places four fingers on four 



press switches and the thumb on one of 
eight press switches. The four finger 
switches operate as the lower four bits 
of the 7 bit ASCII code, selecting the 
group of characters (out of 16 groups) 
that contains the desired character. The 
group contains a choice of eight letters, 
numerals, symbols, etc. The thumb then 
presses the particular switch that selects 
the desired character from the choice of 
eight. A computer is not required to 
operate the terminal. The Writehander 
will directly operate terminals such as 
the Diablo HyType, Teletype ASCII 
modified Selectric, or a video monitor 
that accepts parallel 7 bit ASCII signals. 
Required power is 200 mADC from 5 V 
regulated or 7 to 25 V unregulated. The 
unit connects to the terminal through a 
ribbon cable that has lines for the 7 bit 
ASCII code, a 1 bit fixed parity, strobe 
and acknowledge signals and the power 
and common lines. The price of the 
Writehander is $98 and it can be ob- 
tained from the NewO Company, 246 
Walter Hays Dr, Palo Alto CA 94303." 

Circle 646 on inquiry card. 



Line Printer with Graphic Capabilities 







IKi mt 


_ ^^'**^«^_ .f f 



The Model 160 Malibu Line Printer 
is a commercial grade dot matrix 
machine which operates bidirectionally 
at 165 characters per second and has 
graphics capabilities. The printer's fea- 
tures include logic seeking capabilities 
for fast throughput, reinking rollers (said 
to increase ribbon life up to 50 million 
characters), and jumper selectable pri- 
mary voltage (110 to 220 V, 50 to 60 
Hz). Standard software supports the 96 
character ASCII set, but the user may 
easily change the characters to exotic 
languages, scientific symbols, or what- 
ever can be printed with a 9 pin head. 
The tractor operated paper feed allows 
groups of dots to be placed immediately 
adjacent to one another either hori- 
zontally or vertically, giving graphics 
capabilities at 3000 dot locations per 



square inch. The Malibu accepts paper 
from 4 inch (10 cm) to 15 (37.5 cm) 
inch width and prints up to 132 char- 
acters per line. Normal line feed is 1/6 
inch (0.4 cm), but increments of 1/60 
inch (0.04 cm) are possible under 
software control. All circuitry is de- 
signed into three circuit boards which 
plug into the mother board. An optional 
Altair (S-100) interface card is available, 
making the printer immediately operable 
with many popular computers. An 
RS-232 option with a Z-80 processor on 
board allows the printer to accept serial 
input (up to 9600 bps) or parallel ASCII 
input with handshaking. The Malibu 
printer is priced at less than $2000 from 
Malibu Design Group Inc, 21110G 
Nordhoff St.Chatsworth CA 91311." 

Circle 653 on inquiry card- 




The FUTRA Model 10 Line Printer 
incorporates a belt impact, full character 
(not dot matrix) 80 column printing 
mechanism. The unit operates at a mini- 
mum print rate of 150 lines per minute 
using the 64 ASCII character set or a 
minimum of 84 lines per minute using 
a full 96 ASCII character set and can 
produce up to four copies including the 
original. The input is an 8 bit parallel 
which can be interfaced to a 3P-^S or 
similar interface card. The unit has a 
buffer size of one full line (80 char- 
acters) and a maximum data input rate 
of 75,000 characters per second. 

The Model 10 is priced at $2695 
and comes with pin feed paper handling 
mechanism, format control unit (top of 
form), either 64 or 96 ASCII character 
set and parallel interface. Options are 
an off line test print excercisor, $75; 
and serial interface (RS-232c, 20 mA 
current loop, TTL direct interface with 
1010 byte buffer), $595. Contact 
FUTRA, 3421 Onyx St, POB 4380, 
Torrance CA 90510, (213) 371-8138." 

Circle 583 on inquirv card 

Fast Cassette Interface 




The Wince Cassette Interface dumps 
and loads programs at a data rate of 
2400 bps. It also supports the 300 bps 
Kansas City standard. The unit inter- 
faces directly to a Motorola 6850 ACIA 
and includes an RS232 interface at data 
rates from 150 to 9600 bps. The inter- 
face board is priced at $139 in single 
quantities from Wintek Corp, 902 N 9th 
St, Lafayette IN 47904, (31 7) 742-6802." 

Circle 584 on inquiry card. 



192 



July 1978 ©BYTE Publicilioni Inc 



DIODES/ZENERS 


SOCKETS/BRIDGES 


TRANSISTORS, LEDS, etc. 




1N914 


lOOv 


10mA .05 


8-pin pcb .20 WW .35 


2N2222 


NPN (2N2222 Plastic .10) 


.15 


1N4n05 
1 N4007 


600v 
lOOOv 




1A .08 
1A .15 


14-pin pcb .20 WW .40 
16-pin pcb .20 WW .40 


2N2907 
2N3906 
2N3904 


PNP 

PNP (Plastic - Unmarked) 

NPN (Plastic - Unmarked) 


.15 
.10 
.10 


1N4148 


75v 


10mA .05 


18-pin pcb .25 ww .75 


2N3054 


NPN 


.35 


1N4733 


5.1v 


1 W 


Zener .25 


22-pin pcb .35 ww .95 


2N3055 


NPN 15A 60v 


.50 


1N753A 
1N758A 


6.2v 
lOv 


500mWZener .25 
.25 


24-pin pcb .35 ww .95 
28-pin pcb .45 ww 1.25 


T1P125 
LED Green, 
D.L.747 


PNP Darlington 
Red, Clear, Yellow 
7 seg 5/8" High com-anode 


.35 

.15 

1.95 


1N759A 


12v 




.25 


40-pin pcb .50 ww 1.25 


MAN72 


7 seg com-anode (Red) 


1.25 


IN 5243 

1N5244B 

1N5245B 


13v 
14v 
15v 




.25 
.25 
.25 


IVIolex pins .01 To-3 Sockets .25 


MAN3610 
MAN82A 


7 seg com-anode (Grange) 
7 seg com-anode (Yellow) 


1.25 
1.25 




2 Amp Bridge 100-prv .95 


MAN74A 
FND359 


7 seg com-cathode (Red) 
7 seg conrvcathode (Red) 


1.50 
1.25 










25 Amp Bridge 200-prv 1 .95 








CMOS 






- T T L - 






4000 


.15 


7400 


.10 


7473 .25 


74176 .85 


74H72 


.35 


74S133 


.40 


4001 


.15 


7401 


.15 


7474 .30 


74180 .55 


74H101 


.75 


74S140 


.55 


4002 


.20 


7402 


.15 


7475 .35 


74181 2.25 


74H103 


.55 


74S151 


.30 


4004 


3.95 


7403 


.15 


7476 .40 


74182 .75 


74H106 


.95 


74S153 


.35 


4006 


.95 


7404 


.10 


7480 .55 


74190 1.25 






74S157 


.75 


4007 


.20 


7405 


.25 


7481 .75 


74191 .95 


74 LOO 


.25 


74S158 


.30 


4008 


.75 


7406 


.25 


7483 .75 


74192 .75 


74L02 


.20 


74S194 


1.05 


4009 


.35 


7407 


.55 


7485 .55 


74193 .85 


74L03 


.25 


74S257(8123) 


1.05 


4010 


.35 


7408 


.15 


7486 .25 


74194 .95 


74L04 


.30 






4011 


.20 


7409 


.15 


7489 1.05 


74195 .95 


74L10 


.20 


74LS00 


.20 


4012 


.20 


7410 


.15 


7490 .45 


74196 .95 


74L20 


.35 


74LS01 


.20 


4013 


.40 


7411 


.25 


7491 .70 


74197 .95 


74L30 


.45 


74LS02 


.20 


4014 


.75 


7412 


.25 


7492 .45 


74198 1.45 


74L47 


1.95 


74LS04 


.20 


4015 


.75 


7413 


.25 


7493 .35 


74221 1.00 


74L51 


.45 


74LS05 


.25 


4016 


.35 


7414 


.75 


7494 .75 


74367 .75 


74L55 


.65 


74LS08 


.25 


4017 


.75 


7416 


.25 


7495 .60 




74L72 


.45 


74LS09 


.25 


4018 


.75 


7417 


.40 


7496 .80 


751 08A .35 


74L73 


.40 


74LS10 


.25 


4019 


.35 


7420 


.15 


74100 1.15 


75491 .50 


74L74 


.45 


74LS11 


.25 


4020 


.85 


7426 


.25 


74107 .25 


75492 .50 


74L75 


.55 


74LS20 


.20 


4021 


.75 


7427 


.25 


74121 .35 




74L93 


.55 


74LS21 


.25 


4022 


.75 


7430 


.15 


74122 .55 




74L123 


.85 


74LS22 


.25 


4023 


.20 


7432 


.20 


74123 .35 


74H00 .15 






74LS32 


.25 


4024 


.75 


7437 


.20 


74125 .45 


74H01 .20 


74S00 


.35 


74LS37 


.25 


4025 


.20 


7438 


.20 


74126 .35 


74H04 -20 


74S02 


.35 


74LS38 


.35 


4026 


1.95 


7440 


.20 


74132 .75 


74H05 .20 


74S03 


.25 


74LS40 


.30 


4027 


.35 


7441 


1.15 


74141 .90 


74H08 .35 


74S04 


.25 


74LS42 


.65 


4028 


.75 


7442 


.45 


74150 .85 


74H10 .35 


74S05 


.35 


74LS51 


.35 


4030 


.35 


7443 


.45 


74151 .65 


74H11 .25 


74S08 


.35 


74LS74 


.35 


4033 


1.50 


7444 


.45 


74153 .75 


74H15 .45 


74S10 


.35 


74LS86 


.35 


4034 


2.45 


7445 


.65 


74154 .95 


74H20 .25 


74811 


.35 


74LS90 


.55 


4035 


.75 


7446 


.70 


74156 .70 


74H21 .25 


74S20 


.25 


74LS93 


.55 


4040 


.75 


7447 


.70 


741 57 .65 


74H22 .40 


74S40 


.20 


74LS107 


.40 


4041 


.69 


7448 


.50 


74161 .55 


74H30 .20 


74S50 


.20 


74 LSI 23 


1.00 


4042 


.65 


7450 


.25 


74163 .85 


74H40 .25 


74S51 


.25 


74LS151 


.75 


4043 


.50 


7451 


.25 


74164 .60 


74H50 .25 


74S64 


.15 


74 LSI 53 


.75 


4044 


.65 


7453 


.20 


74165 1.10 


74H51 .25 


74S74 


.35 


74LS157 


.75 


4046 


1.25 


7454 


.25 


74166 1.25 


74H52 .15 


7481 12 


.60 


74LS164 


1.00 


4049 


.45 


7460 


.40 


74175 .80 


74H53J .25 


74S114 


.65 


74 LSI 93 


.95 


4050 


.45 


7470 


.45 




74H55 .20 






74LS367 


.75 


4066 
4069/74 C04 


.55 
.25 


7472 


.40 










74LS368 


.65 










4071 


.25 




IVICT2 .95 LINEARS, REGULATORS, etc. 






4081 


.30 




8038 3.95 


LIVI320T5 1.65 


LM340K15 


1.25 


LM723 


.40 


4082 


.30 




LM201 .75 


LIVI320T12 1.65 


LM340K18 


1.25 


LM725N 


2.50 


MC 14409 14.50 




LM301 .45 


LM320T15 1.65 


LM340K24 


1.25 


LIVI739 


1.50 


MC 14419 


4.85 




LIV1308 (Mini) .95 


LM324N 1.25 


78L05 


.75 


LIVI741 (8-141 .25 1 


4511 


.95 




LM309H .65 


LM339 .75 


78L12 


.75 


Ll\/1747 


1.10 


74C1 51 


1.90 




LM309K(340K-5>85 


7805 (340T5) .95 


78L15 


.75 


LM1307 


1.25 








LIV1310 .85 
LM311D(Mrni) .75 


LM340T12 .95 
LM340T15 .95 


78M05 
LM373 


.75 
2.95 


LM1458 
LM3900 


.65 
.50 


9000 SERIES 




9301 .85 


95H03 


1.10 


LM318(Mini) 1.75 


LM340T18 .95 


LM380(8-i4PiN).95 


Ll\/I75451 


.65 


9309 .35 


9601 


.20 


LM320K5{7905)1.65 


LM340T24 .95 


LM709(8,i4PiN).25 


NE555 


.35 


9322 .65 


9602 


.45 


LM320K12 1.65 


LIVI340K12 1.25 


LM711 


.45 


NE556 
NE565 
NE566 
NE567 


.85 

.95 

1.25 

.95 


MICRO'S, RAMS. C 


PU'S, 






E-PRC 

74S188 3.00 
1702A 4.50 


)MS 

8214 
8224 


8.95 
3.25 


INTEGRATED CIRCUITS UNLIMIT 


ED 








MM5314 3.00 


8228 


6.00 


7889 Clalremont Mesa Boulevard, San Diego, California 92111 




MM5316 3.50 
2102-1 1.45 


8251 
8255 


8.50 
10.60 


(714) 278-4394 (Calif. Res.) 


SPECIAL 
DISCOUNTS 


2102L-1 1.75 


8T13 


1.50 


All orders shipped prepaid No minimum 


Total Order 


Deduct 


2114 9.50 
TR1602B 3.95 


8T23 
8T24 


1.50 
2.00 


Open accounts invited COD orders accepted $35 -$99 


10% 


TMS4044- 9.95 


8T97 


1.00 


Discounts available at OEM Quantities California Residents add 6% Sales Tax *1^V ' Z.^^ 


15% 




2107 


3-4 4.95 


All IC's Prime/Guaranteed. Ail orders shipped same day received. 


saui - !t>iuuu 


20% 


8080 8.95 
8212 2.95 


2708 
Z80P 


9.50 
10 8.50 


24 Hour Toll Free Phone 1-800- 854-221 1 American Express / BankAmericard / Visa / MasterCharge 



Circle 180 on inquiry card. 



BYTE luly 1978 



193 



/g 



aCfipif CT Mates with two rows ot 025" sq. or 
OUulVCI dia posts on patterns of 100" 
lilR/IDCDC c^eoters and shielded receptacles 
JUIVIr tnO Probe access holes in back. Choice 



Part No. 

924003-1 8R 
924003 -06R 
92400S-18R 
924005 -06R 
924006-1 8R 
924006-06R 



of 6" or 18" length. 
No. ot Contacts Lengtl) 

26 18" 
26 6" 

40 18" 
40 6" 

50 18" 
50 6" 



Price 

$ 5 38 ea. 
4.78 ea. 
8.27 ea. 
7.33 ea. 
10.31 ea. 
9.15 ea. 



HIIIMPFR ^"'"^^ '° ^'' tioards for instant 
JW"'' f" plug-in access via socket-connector 
Ijr JinpoQ jurnpers. 025" sq posts Choice 
nCMUCno of straight or right angie. 



Part No. 

923863-R 
923873 -R 
923865-R 
923875-R 
923B66-R 
923876 -R 



No. ot Posts Angle 



26 
26 
40 
40 
50 
50 



straight 
right angle 
straight 
right angle 
straight 
right angle 



Price 

SI .28 ea. 

1 52ea 
1.94 ea 
2.30 ea. 
2.36 ea. 

2 82ea. 




DIP JUMPERS 

Males with stanttard 1C sockets 

24" lengtt) • Fully Assembled i Tested 

PRICE 

t 1.92 
3.02 



40 



m end 
sgl end 



924106-24 
924112-24 
924116-24 
924122-24 
924126-24 
924132-24 



334 
330 
S.20 
553 



Also Available in 12" and 36" lengths 



32 



CYlft 

CY1.84 

CY2A 

CV201 

CY2 50 

CY3.27 

CY3.57 

CY3A 

CY491 

CY7A 

CY5.18 

CY6.14 

CY6.40 

CY6.55 

CY12A 

CY14A 

CY19A 

CY18 43 

CY22A 

CY30A 



CRYSTALS I 

TKESE FREaUENCIE!; ONLY J; 
FREQUENCY CASE 

1 00OMH2 

1 8432MH2 

2 0OOMH2 
2.010I^Hz 
2500MH2 

3 2768MH2 
3579545MH; 
4.000MH! 
4.916MHz 
5.000MHz 

5 185MHz 

6 144MH2 
6400MHz 
6 5536MHz 
10 000MH2 
14 3I818MH; 
18.000MHz 
18.432MHz 
20 000MH2 
32 OOOMHz 



HC33 


5 95 


HC33 


595 


HC33 


595 


HC33 


1.95 


HC33 


4.95 


HC33 


495 


HC33 


495 


HC18 


4 95 


HC18 


4 95 


HC18 


4.95 


HC18 


4 95 


HCt8 


4 95 


HCie 


4 95 


HC18 


4.95 


HC18 


4.95 


HC18 


495 


HCt8 


4.95 


HC18 


495 


HC18 


4.95 


HC18 


4 95 



TRIMMERS 



10MM size trimmers -.394" Dia. 

Part No. 1-9 10-24 25-49 100 + 
TR-11 (valve) 35 .30 25 20 

Resisrance values . 10Q. 500 IK ?K. 5K 10K ?0K. 50K. lOOK. ?00k 1 meg 



TRIMPOTS 

Single-Turn - 1/2 Walt 

Square - Top Ailjust - 3/B" Size 
Pan No. 1-9 10-24 25-49 50-99 

63P(value) .99 .89 .80 .70 

Resistance Values -50. too 500 IK,2«,5K. 10K.?OK 50K lOOK, 200k, 500K, 1 meg 



^j 



15-Turn - 3/4 Watt 

Rectanguiar Side Adjust 3/4" x 1/4" Size 
Pari No. 1-9 10-24 25-49 50-99 

43P(value) 1.35 1.25 1.20 1.15 

50. 100.500, IK, ?K,5k, I0K.Z0K,50K, lOOK, 200K, 500K, 1 ™g 



1/16 VECTOR BOARD 



Par! No 
64P44 0S2XXXP 
169P44 062XXXP 
64P'14 D62WE 
B4P4-1 062Wt 
169P44 062WE 
t69P84 062 WE 
169P44 062WEC1 



Rsn 


?07 


fiSO 


?m 


7 00 


hlM 


7,00 


9 23 






Model P180 Includes 2-100' spools #28 AWG 
wire wrap wire 



Supplies insul. 
pingandpreci 

Model P180 



$24.50 



REPLACEMENT WRAP BIT 
forPISOSlit N Wrap 
No. P180A $12.95 each 



Replacement wire-wrap 
wire for P180 #28 AWG 
(pkg ot 31 $2.75 each 

W2B-2-A green W28-2-B red 

W2S-2-C clear W2a-2-D blue 



INSTRUMENT/ 
CLOCK CASE 

IniectJon molded unrt. 
Complete with red Oe;el 



$3.49 




CPU 
8080A CPU 



MICROPROCESSOR COMPONENTS 



8212 
8214 
8216 
8224 
8228 
8251 
8255 



8-8it Input/Output 
Pfionty Interrupt Control 
Bi -Directional Bus Driver 
Clock Generator/Driver 
System Controtler/Bus Driver 
Prog Comm. Interlace 
Prog Periph. Interlace 



$29.95 CDP 1802 CPU 

10,95 Z80 CPU 

4.95 3650 MPU 

7.95 MC6800 MPU 

4.95 MC6810API 126 x 8 Static Ram 

5.95 MC6820 Penph. Interlace Adapter 

5.95 MC6821 Periph, Interface Adapter 

9.95 MC6830L8 1024x8 Bit ROM 

10-95 MC6850 Asychronous Comm. Adapter 



S19.95 
24.95 
26.50 
19 95 
5.95 
7.95 
11.50 
14.95 
14,95 



[The Incredible 
"Pennywhistle 103" 



25B 



2101 

2102 

2107/5280 

2111 

?112 

2114 

2)14L 

2114-3 

21UL-3 

7489 

aioi 



21L02 
74200 
9342! 



FUM'S 

1 Static 
X 1 Dynamic 
4 Sialic 
« T Static 
I 1 Dynamic 
: 4 Static 
I 4 Sialic 
1 Slatic 450n5 
1 Sialic 450ns Low Power 
1 Static 300i!s 
1 Static 300(15 Low Power 
4 Sialic 
[ 4 Static 
( 4 Static 
4 static 



S ! 49 



MK4027 (UPD4U) 1 
MK4116iUPD416| 1 
TMS4044-45NL 4 



DYNAMIC 16 PIN 
DYNAMIC 16 PIN 
STATIC 



"STna 



2513(2140) 
2513(3021) 
2516 
MM5230N 



1802M 
!80M 
2e50M 



ROMS 

Characlei Generator (upper case] 
Cli a racier Generator (lower case) 
ChariCier Generator 
2048 Bil Read Only Memory 

USER MANUALS 
CDP1S02 Manual 
2S0 Manual 
2650 Manual 



1702A 

5203 

B2S23 

82S115 

B2S123 

743287 

2708 

2716 T.I 

2716 Intel 

6301-1 

6330-1 

;41li6 
7418H 

MM5013N 

MM5016H 

MM5017N 

2504T 

:?518 

■^519 

2522 

2534 

2525 

2527 

2528 

2529 



2048 X 
204B « 
32x8 



16K 



PROMS 

Famous 

Famous 

OpenC 

Bipolar 

Tristdte 

Static 

EPROM 

EPROM 

EPflOM 

Ui Stme Hi(jc)..(; 
j6 I 1 Onen C Bmnij' 

12 > ' ni Ocen CoHecioi 

56 1 1 TTL Open Collaaor 

SHIFT REGISTERS 
1024 Bit Accumulator Dynamic 
500/512 Bil Dynai-ic 
Dual 50O,'5l2 eit Uvnamic 
1024 Dynamic 
Hex 32 BiI Sialic 
net ■lO Bii Static 
Dual t.i: Bil Siaik' 
512 Oynamtf 
1024 Dynamic 
Dual 256 Bit Static 
Qua' 250 Static 
Dual 24n Bit SUlic 
OuaU 80 'in Static 
1024 Static 
Fito" 
4X4 Rflgistfi' 

UARTS 
3QK BAUD 



S 5 95 



TELEPHONE 
KEYBOARD CHIPS 

Ay-5-9100 $14 95 
flY-5-9200 14 95 
Ay-5-9500 4 95 
Ay-5-2376 14 95 
HD0165 7 95 

74C922 9.95 



SPECIAL REQUESTED ITEMS 



(CM CHIPS 

ICM7045 E24.95 
ICH7205 19 95 
ICM7207 7 50 

ICM7208 19.95 
ICM7209 6 95 



NMOS READ ONLY 
MEMORIES 

MCM6571 S13M) 
MCM6574 13 5(1 
MCm57^ 13 50 



MISCELLANEOUS 



MC3061P 
'jICUOBI ' 
"1[;i-lU8L8 



PARATRONICS 

Logic Analyzer Kit 
Model 100A 

$229.00/kit 



pV GAME CHIP SET 

I AY-3-3500-1 Cliia:intl 2.01D MH2 Crystal $7.9S[ 



95H90 
s:'-- 00 .'set 



I I I I I 



1111 
• «■« 1 



Analy/es any type ot digital system 

Cfi'-'ci'^ data rates in excess o( 8 

million words per second 
I Trouble Stiool TiL. CMOS, OIL. RTL 

Schonky and MOS tamilies 
. Displays 1 6 logic states iiplo 8 digits wide 
I See ones and zeros displayed on your 

CRT. ocial 01 hrtxadpctmal \o«"'^t 

■ Tests circuits unOei acr'jai ope-aling conditions 

■ Easy to assemble — comes with step-by-step construction 
manual which includes 80 pages on logic analyzer operation. 

(Model 100A Manual ■ $4 951 



,»^r'|^t1HiP""» 



Some applications are 

- Troubleshooting microprocessor 
address, mstruction, and data flow 

~ Examine contents ot ROMS 

- Tracing operation of control logic 

- Checking counter and shift 
register operation 

- Monitoring 1/0 sequences 

- Veritying proper system operations 
during testing 



PARATRONICS TRIGGER EXPANDER - Model 10 

Adds 16 additional bits. Provides digilsl delay aid qualilication of input cl 
and 24-bit trigger word, — Connects direct to Model lOOA for i ntegrated ui 



I 1G Kit - S229.00 



Ba»plate - S9 95 

Model 10 Manual - 




3Vi-Dlglt Portable DMM 

• OverloaO Protected 

• 3 high LED DiSDlay 

• 8aMerv or AC oppralion 

• Aiilo 7e;oiny 

• lin-j IVa I Cfiin ffiSolulrO'i 

• Ovtiange ifdding 

• 10 meg input impendence 
■ DC Accuracy l-o typical 
Rang*s; DC Voltage - 0-lOOOV 
AC Voliage O-lMOV 

Freq Responw 50-400 h2 
DC/AC Current 0-lOOmA 
ResislacCB 0-Ki meg ohm 
Size 6 ■: .44 < ? 

Accessories: 
AC Adapter BC-28 S9.Q0 
Rechargeatile 

Batteries BP-28 20.00 
Carrying Case LC-28 7.50 



"95 



100 MHz 8-Digit Counter 

20 Hz-100 MHz Range , four power souces, i e 

battenes ' 10 or PZOV witn 

* charger l?V w tti auio 

lighter adaqter and eiteinal 

7,2-lOV power supply 

"'x-io" $134.95 



• 6' LED Display 

■ C rysta I -cpnt rolled timet 

• Fully Aulomatie 

■ Portable — completely 
self -contained 



« 5 63' 



ACCESSORIES FOR MAX 100: 

MotillB Chargar Eliminator 

use power Iron) car bahery Model 100 — CLA S3.9S 

Charger/Eliminator 

use 1 10 V AC Moilel 1D0 - CAI S9.35 



63- Key Unen coded 



I KEYBOARDS I 



Hexadecimal Encoder 




This Is a 63-key, terminal keyboard newly 
manufactured by a large computer manufac- 
turer. It is unencoded with SPST keys, unat- 
tactied to any kind ot PC board. A very solid 
molded plastic 13x4" base suits most applica- 

tion. IN STOCK $29.95/each 




19-key pad includes 1-10 keys, 
ABCDEF and 2 optional keys and a 
shift key. $10.95/each 



$5.00 IVIinimum Order - U.S. Funds Only 
California Residents - Add 6% Sales Tax 



Spec Sheets - Ki 

I978A Catalog Avallable-Ssnd 3S< stamp 




J Sameco 



PHONE 

ORDERS 

WELCOME 

(415) 592-8097 



MAIL ORDER ELECTRONICS - WORLDWIDE 

1021 HOWARD AVENUE. SAN I:ARL0S. CA 94070 

Advertised Prices Good Tliru July 



$129.95 



Kit Only 




The PennywlHStle 103 is CKRshle ol recorrlmg ^nXi to ana Trom audio laps withDu: 
nilical soeeil requireinenls lor tue fetonler and il is able lo roinmiiincate liracHv 
with another modern and teminal lor teleptione tiamimnq snri coimmitiicabon; 
toi ttie deal In addition , it is free ot critical aHju^lieiits am is tiiiill with non -precision 
readily availaQle parts 
Data Transmlnian Method . , Frequency Shitl Keying Itill-ilupiex ihallOuole' 

selecJaDtei 

MaKimum Data Rata 300 Baud 

Dala Format , , Asynctironous Seiial netufn to 'nsrlt level lequnei 

hetween eacb cbaracteri 
Receive Channel Freijuencies . .2025 Hz lor space 3?35 Hz lor narK 
Transmil Ctiaitnel Fteguencies . .Swilcn selectalile Low inornali lQ7fi so^ce 

1370 TiatW High 025 spate "i'-'S km 
fleceivG Sensilivity .46 ilb ti accousiically en..' , i 

iio-ninal ftiljustsbie I'O i' t ih n 



Receive Frequency Tolerance 
Oigital Data Inlerlace 



to .'ll 'II 

.Frequency reterence auion^licaiiv .t.i|.isls 

alio* 'or opeiation belwee'i 1800 h/ rfiti ?.lf)D H 
.EIA RS-33?C or ?Q ■nA cufiRm iQOi t'Bi'KWi 

opioisolaled and iion w\fu 

120 VAC single Dhasf! 1 



..All c 



I All c 



■ipotie 



■myle b 



R"qiiiie . fl V0^^ Audio Oscillator fieguency Goiintef and O' QscHmscope te 




the 3 



rd 



Hand 

$9.95 each 



'Leaves two hands 'ree (nr 

working 
* Clamps on edge ot bench, lable 

or work bench 
■ Position board on angle or flat 

position fo' --oldenng or clipping 
' Slufrty .-^iii tii'ium consfr^'Ciion 

tor hobbyist, -nanulacturer or 

.school rooms 



DIGITAL STOPWATCH 



■ BNgni 6 Digii LEO Display 

• rtmes 10 S9 minutes 59 59 - 

• CfVEtai Controlled Time Ba't 

■ Tfiree StopwatcWs m One 

limes Single Event — Split S Tiyii 
.Sim4 5 t? 15 « 90 i4';ounceii 

• Uses 3 Penlite Cells 

Kit - $39.95 

Assembled — $49.95 
Heavy Duly Carry Case $5.95 



Stop Watch Chip Only (7205) (19 95 




3y2DIGIT DPM KIT 



W 



j^W 



New Bipolar Unit • Auto Polarity 

• Auto Zeroing • Low Power 

. .5" LED • Single IC Unit 

Model KB500 DPM Kit $49.00 

Model KB503 5V Power Kit $17.50 




JE700 CLOCK 



MAN n I] h 1] f "lout diid 

KIT ONLY $16.95 



JE803 PROBE 

Ifie Lo:|i{, Prnlif .s ,i unit *ni( ri iv fo' tne -tiosi p.ir' 
indesoenjibte m irouDie ihooliig logic lamiiips 
ni DH RlL CMOS It de'ivc'; tne oowei n 
needs to oceiale directly o't ol ine riicuil unoei 
tesi dia*inija scani 10 mA mai- ituses^MANi 
readDui to indicate any n' trie toiiowinq slates 3^ 
tnesesymUois 'Hi i iiOWi mPuLSl' P Tus 
Probe can dPiect niQ*! ttpauenr-y ouise<. m 45 Mh? 
II c?r> I tip used ,11 MOS Ipvci-, ii- 



$9.95 Per Kit 

printed circuit board 







VI 5V 1A Supply 

This IS a standard HL oowf supply uS'ing tbe well knni 
LM309K regulator ^C to proviOe a soltO 1 AMP o' curreni ai 
volts We try to make things easy lot yoo by p'Ovidn 
everyttiing you nepc! in one package including Ihe Itanlwa 

'" °°' JE225 $9.95 Per Kit 



PROTO BOARDS 



PROTO BOARD 6 

S15.95 

[6 long X 4 wide) 




wnHnnninmi 



PROTO CLIPS 

14 PIN S4 50 

16 PIN 4 75 

24 PIN 8 50 

40 PIN 13.75> 



194 BYTE July 1978 



SN7400N 
SN740m 
SN7402N 
SN7403N 
SN7404N 
SN7405N 
SN7406N 
SN7407N 
SN7408N 
SN7409K 
SN7410N 
SN74nN 
SN741;N 
SN7413N 
SM7414N 
SNM16N 
SN7417N 
SN7430N 

SN7421N 
SN74Z2N 
SN7423N 
SN74Z5N 
SN7426N 
SN7427N 
SNM?9N 
SN7430N 
5N7432N 
SN7437N 
SN743SN 
SN7439N 
St4744(M 
SN7441N 
SN7442f( 
SN7443N 
SN7444N 
SNT44SN 
SN744eN 
SN7447t, 
SN7448M 
SN74S0N 
SN74S1N 
SN74S3N 
SN7454N 
SN7459A 
SN7460N 
Sn;470N 



CD4000 
CD4001 
CD4M2 
C04006 
CIM007 
CD4009 
CO40I0 
C0401 1 
CD401? 
CO4013 
CD40)4 
CO4015 
CD4016 
CO4017 
CD401B 
CD4D19 
CD4020 
CD40J1 

C04o;2 

C04K3 
CO4024 
Cn402S 
CD40?6 



74C02 

74CM 
74C08 
7-1C10 
74C14 
74C20 
74C30 
74C4! 
74048 
"IC73 



lM3uU»i 

LM301H 

IM301CN 

LM302H 

I.M304H 

IM305H 

LM307CN H 

LM30eM 

LM308CN 

LU309H 

LM309K 

LM3tKN 

LM3ltH 

LM3nN 

LM317K 

LM318CN 

LM319N 

LM320K-& 

LU320K-5 2 

LM3raK-12 

LM320K-15 

LM320K-18 

LM320K-24 

LM3MT.5 

LM3aT-5 2 

LM320T-8 

LM3!l)T.t2 

LM3MT-15 

LM320T-ia 

LM320T-24 

LM323K 5 

LU324N 

LM339N 

LM340K-5 

LM340K-6 

LM340K-8 

LM340K-12 

LM340K IS 

LM340K-1B 

LM340K 24 

LM340T-5 



7400 TTL 



SN7472N 

SN7473N 

SN?474N 

SN7475N' 

SN7476N 

SN7479N 

SN74eON 

SN74e2K 

SN7483N 

SN7485N 

SN74B6N 

SN74B9N 

SN7490N 

SN7491N 

SN7492N 

5N74g3N 

SN7494N 

SN7495N 

SN7496N 

SN7497N 

SN74tOON 

SN74I07N 

SN74I09N 

SN74116N 

SN74121W 

SN74122N 

SN74I23N 

SN74125N 

SN74126N 

SN74132fc 

SN74136N 

SN 74 14 IN 

SN74142N 

SN74143N 

SN74144N 

SN74145N 

SN74I47N 

SN74t4aN 

SN74150N 

SN7415tN 

SN74I53N 

SN74154N 

SN74155N 

SN74157N 



C/MOS 



CD402e 
CD4rr?q 
CD4030 
CO4035 
CD4040 
CD4041 
C04042 
C04043 
C04044 
CO4046 
CD4047 

ca*tm 

CD4049 
C04050 
CD4051 
CD4053 
CD4056 
CD4059 
CD4060 
CD4066 
CO4068 
CP4069 



74C00 



74C89 
74C90 
74C93 
74C95 
74C107 
74Ct51 
74C154 
74C157 
7-1C160 
74C161 



300 

2 15 

3 ?5 
3^5 



LINEAR 

LM340T 8 ' 25 

LM340T 1? 1 25 

LM340TI5 1 25 

IM340T.16 1 25 

LM340T-24 I 25 

LM350N 1 00 

LM351CN 65 

LM370N 1 15 

lM3r3N 3 25 

LM377N 4 00 

LM380N t 25 

LU380CN 99 

LM381N 1 79 

LM382N t 79 

NESOIN B 00 

NE510A 6 DO 

NES29A 4 95 

NE531H 3 00 

W536T em 

NE540L 6 00 

NE55DN 1 30 

NESSSV 99 

NE556 99 

NEseoe 5 00 

NE56ie 5 00 

NES628 5 00 

W565H 1 75 

NE£fi5N 1 25 

NE566CN 1 75 

NE567H 1 25 

NE567V 99 

NE570 10.50 

LMr03CN/H 45 

LM709H .29 

LM709N 29 

LM710N 79 

LM71IN 39 

LM723H 55 

LM723N 55 



'^B 



3N74160N 
St474161N 
SN74162N 
SN74163N 
SN74164N 
SN74165N 
5NM166N 
SN74167N 
SN74170N 
SN74172N 
SM74173N 
SN74174N 
SN74176N 
SN74176N 
SN74177N 
SN74179N 
SH74iaON 
5N74181N 
SN74182N 
SN74t84N 
SN74185N 

SN74iaaN 

SN741SeN 
SN74190N 
SN74i9tN 
SK74192N 
SN74193N 
SN74194N 
SN74195N 
SN74196N 
SN74197N 
SN74198N 
SN74199N 
SN74200N 
SN74^51N 
SM74279N 
SN742B3N 
SN74284N 
SN742B5N 
SN74365N 
SN74366N 
SN74367N 
SN7436BN 
SN74390N 
SN74393N 



C04070 

CD407I 

CO4072 

CD4076 

CD4081 

004082 

CO4093 

C04098 

wet 4409 

MC14410 

MC144n 

MCU4t9 

MC14433 

UC14506 

MCI 4507 

MCI 4563 

MCI 4583 

CO4508 

CD4510 

CD45n 

CD45I5 

CD4518 

CD4520 

CD456 



BUGBOOK® 

Continuing Education Series 




S17.00 par tat 

fits Msigncd to 



THE S5S nMER APPUCATIONS 
SOURCEBOOK WITH EXPEWMENTS 
bf HMirdM. Barlln W3HB 



jrjpus 

pho'ogrsDfiV. 



THIS ifoiurrw Hill intiodura you tD in< tituilous wm c^p — tni 
inlgpfm Mnntsn diu ttrirunSs dc ind your micocompuU' 
curiifli loopj. tnil th« RS IIK inlerfKt sbndarii Piniculifly 

fT05 

■M, Wt4HYJ. MwMui k. IHm 
Hare IS the tnwli inn puts i all logWu' BesKHs nivmo muctt > 
(MM ire Dwr imre arc i saxes ol natnmtnis rn lafiy^ tne ruMr comtfatety ItlHOW tna 
Xidy 10 go BOW cfuo p.n Oy p« and mlroUUMS you 10 ma Miit 60 rmcrocompum 
arcuils D3fiy un-qua lastt* iniartjcaa syflam It is ^acofimeralafl iha — ■ - — "" "■■ 



KM BUGROOK III 






1e 8UDB0OKS I & II 



WITi euGBOOK III 



IHSTRUCTOH'S MANUAL 

Nacasuiv N>i insirucnO'i ol Bugbooii > and i 
enpanntants suggesnansloitu'lher tMing p 
dliilil aiedrDflics * musl lo' sal'-laacning im 



BUGIDOK V and VI 



S19.D0 H' nl 



OP AMP MANUAL by Hmird M. Birlln W3HB tg.QO gugbooK vi loun). 



at 2S 



S3.00 t, OnM ~G Urawi, l>IMr H taqr, JMMhta A. tltM 

J^J']? EipanmanS ui i»||m Bacl'omcs aOSOA micnicomouiar prograip 
WMA mcrocomuula' inlailidng *n intaijiJtBO iMKoacli lo salt 
tiasic digital g4«c1ron>cs. Dteaaboiriling 3M 8060* mtarlacmgipFognmrning 

- —-' - was tfia digital concapW ol BuflboM V into a treMirwni ol 

nuKr orogiaipming tnfi interfacing Dalai) 9r Utornarv 



T4Cie5 

74Ct64 
74C173 
74C1 92 
74C193 
74CI95 
74C922 
74C923 
74C925 
74C926 
80095 



LM733N 
LM739N 
LM741CM 
LM741CN 



LM74 



)4N 



LM747H 

LM747N 79 

LM748H 39 

LM748N 39 

LU1303N 90 

LM1304N 1 19 

IM1305N 1 40 

LM1307N 85 

LMiSlON 2 95 

LM1351N '65 

LMI4UN 1 75 

l.M145eCN.'M 59 

MC1488 1 95 

Mcuag t 95 

LU1496N 95 

LM 1556V 1 75 

MC1741SCP 3 00 

LM2901N 2 95 

LM3053 t 50 

LM3065N 69 
LM3900N(3401| 49 

LM3905N 89 

LM3909 1 25 

MC5558V 1 00 

lM7525N 90 

LM7SMN 75 

80386 495 

LM75450 49 

75451 CN 39 

75452CN 39 

75453CN 39 

75454CN 39 

75491 CN 79 

75492CN 89 

75494CN 89 

nC415i 5 95 

RC4I94 5 95 

RC4195 4 49 



OBUO 

BD80 mtgi 

aisa<nW|i languipt programs 



jf tnlanng. 4ebui)gi"9 '"'' storing 



U CMOS-M - DESIGNERS PRIMER 

AND HANDBOOK Naw axpindad vanion 



%t.SO 



COMPLETE MANUAL FOR OIGITAL CLOCKS by John Waiu and John Briuks 

Famiiidrizes lecnmcis.-i oi riobbyis! *itti basic meones ijemna oigitat cloWs Includes trouWe stiooling gmOes Sasic 
clijiaclerisiics of clocks, soldefing tBChniques. clock component data sJieeis anfl construclioti tips. 



■4LS0O 
. 4LS02 
74LS03 
74LS04 
74LS05 
74LS08 
74LS10 
74LS13 
74LS14 
74LS20 
74LS26 
74LS27 
74LS2a 
74LS30 
74LS32 
'4LS40 
74LS42 
74LS47 
74LS51 
74LS55 
^741573 



74LS00 TTL 



74LS74 
74LS75 
74LS76 
74LS83 
74LSa5 
741586 
74LS90 
74LS92 
74LS93 
74LS95 
74LS96 
74LS1D7 
74LS109 
74LS112 
74LS123 
74LS132 
74LS136 
74LS138 
74LS139 
74LS151 



74LS155 
741S157 
74LS160 
74LSibl 
74LS16? 
74LS163 
74LS164 
74LS175 
74LSI8I 
74LS19C 
74LS19I 
741S192 
74LS193 
74LS194 
74LS195 
74LS253 
74LS257 
74LS260 
741.S279 
741S367 
74LS368 
74LS670 



XC209 
XC209 
XC209 
XC209 

XC22 
XC22 
KC22 
XC22 
SSL 22 



Green 
Oiange 
Veiiow 
TOO <ha 

R«J 
G'een 
Vellow 
OfBoge 



DISCRETE LEDS 



XC526 
)(C526 
XC526 
XC526 
XC526 



XC556 
XC556 
XC556 
XC556 
XC556 
XC556 



Green 
YellOM 
Oiange 



.190" dia 

Red 5 -SI 

Gteen 4 Si 

Velio* 4 SI 

Oranoe 4/Sl 

.085' dis. 
MV50 Red 6^1 

ITT dIa. 
MV10 Had 4/S1 



Fiat 



s.'siw 



DISPLAY LEDS 



MAN 1 
MAN 2 
MAN 3 
MAN 4 
MAN 52 
MAN 71 
MAN 72 
MAN 74 
MAN 81 
MAN 82 
MAN 84 
MAN 3620 
MAN 3630 
MAN 3640 
MAN 4610 
MAN 4640 
MAN 4710 
MAN 4730 
MAN 4740 
MAN 4810 
MAN 6610 
MAN 6630 
MAN 6640 
MAN 6650 



POLARITY 

Common Anode -red 
5 I 7 DolMitnx-red 
Common Cainode-red 
Common Calhode-red 
Common AnoOa -gteen 
Common Anode- ret) 
Common Anode -red 
Common CatlwdeieO 
Common Anode -ye I k)* 
Common Anode -yelUoi 
Common Cathode -yelkiw 
Common AnolB -orange 
Comtnon Anijae-orange • I 
Common CatMOeHMsnge 
Common Anode-orange 
Common Cathode -orange 
Common Anode-red -i 
Common Anode -red 
Common Callwde-'eO 
Common Anode -yettow 
Common Anode -orange -D D 
Common An ode -orange 
Common Cathode -orange- D 
Common Ca I hoOe -orange ■ 
Common Anode -ofange 



560 



TTPE 

MAN 6660 

MAM 6710 

MAN67M 

MAN 6740 

MAM 6750 

MAN 6760 

MAN 6780 

OL70i 

OL702 

0L704 

DL707 

DL741 

DL746 

DLr47 

0L749 

01750 

DL33B 

FN070 

fND359 

fND503 

FN0507 

50B2-7300 

5082-7302 

5082-7304 

5082-7340 



POLAMTV 

Common Caltiode -orange 
Common Anode-red -D.D 
Common Anode-reO * 1 
Common Calfwde-red-O D 
Common CathoiJe-red • 1 
Common Anode -red 
Common CattvxJe-red 
Common Anode-red =1 
Common Cattiode-red 
Common CatHde-red 
Common Anode -red 
Common Anode -feO 
Common Anode-reO t i 
Common AnoOc-red 
Common Cathode -red = 1 
Common Caihode-red 
Common Cathode -red 
Common CattMKJe 
Common Anode 
Common Cathode (FNDSOO) 
Common Anode (FN0510I 
4 X 7 Sgl DIgit-RHDP 
4<7Sgl. Digil-LNDP 
Oyerrange cti,iracier ( - 1 1 
4 t 7 Sgl Oigil'Hexadecimai 



RCA LINEAR 

CA3013 2.15 CA3082 2 00 

CA2023 2.56 CA3083 160 

CA3035 248 CA3086 85 

CA3039 1,35 CA3089 3.75 

CA3046 1 30 CA3130 1 39 

CA3059 3 25 CA3140 1 25 

CA3060 3 25 CA3160 1,25 

.85 CA3401 49 

2.00 CA3600 3.50 



CA3080 
CA3081 



CALCULATOR CHIPS 
AND DRIVER 

FCM3617 S5 00 

MM5-25 2 95 

MM5736 t 95 

MM573B 295 

OMa864 2 00 

DM8865 1 00 

75 
75 
7 95 



CLOCK CHIPS 



WIRE-WRAP KIT — WK-2-W 
WRAP . STRIP . UNWRAP 

• Tool tor 30 AWG Wire 

• Roll ol 50 Ft, White or Blue 30 AWG Wire 

• 50 pes eadi r , 2 , 3 « 4 lengths 
pre-stnpped wire 

$12.95 




WIRE WRAP TOOL WSU-30 
WRAP • STRIP • UNWRAP $6.95 



WIRE WRAP WIRE — 30 AWG 

25 ft. mm, $1,25 50ft $1,95 100 ft $2.95 lOOOtt $1500 
SPECIFY COLOR — White - Yellow Red - Green - Blue - Black 



WIRE DISPENSER — WO-30 

• 50 f1, roll 30 AWG KYNAR wire wrap wire $3.95 63. 

• Cuts wire to desired length 

• Stnps 1" of insulation Specify — Blue- Yellow -Whtte -Red 



REPUCEMENT DISPENSER SPOOLS FOR WD 30 

Specify blue, yellow, white or red $1.98/ipool 



MM5309 
MM53n 
MM531? 
MM5314 
UM5316 
UM5318 
MM5369 
MU5841 
7001 



14 Din ST S27 

16 Din SI 30 

IB Din ST 35 

?4 pin ST 49 



: SOLOERTAIL — LOW PROFILE (TIN) SOCKETS 

I so 1M ' ^4 

20 OTW 28 pin LP 45 

27 36 pin LP 60 

30 SOLOERTAIL STANDARD (TIN) ^o d" lp 63 

28 pin ST S 99 



9374 - /-segmenj liti driver 



40 pin SI 
SOLOERTAIL STANDARD (GOLD) 



J^ 40pinSG 1 

WIRE WRAP SOCKETS (GOLD) LEVEL #3 

35 ^^^^^ I^HI D'h WW 



50 PCS 

ASST. 1 
ASST. 2 
ASST. 3 



RESISTOR ASSORTMENTS $1.75 PER ASST. 



66 OHM 82 OHM 100 OHM 120 OHM 150 OHM 

ISO OHM 220 OHM 270 OHM 330 OHM 390 OHM 

470 OHM 560 OHM 680 OHM 820 O™ 1K 

1 2K 1 SK 1 8K 2 2K 2 7K 

3 3K 3 9K 4 7K 5 6K 6 8K 



lOOK 
270K 



330K 
620K 
2 2M 
5 6M 



ASST. 8R Includes Resistor Assortments 1 -7 (350 PCS,) 



1/4 WAH 5% 50 PCS 

1/4 WAn 5% 50 PCS 

1/4 WAH S% SO PCS. 

U4 WAH i-x. 50 PCS. 

1/4 WAH 5% MPCS. 

1/4 WATT 5% 50 PCS. 

1/4 WAn S% SOPCS. 

$9.95 ea. 



$5.00 Minimum Order- U.S. Funds Only 
California Residents - Add 6% Sales Tax 



Spec Sheets - 2U 

1978A Catalog Available-Send 35^ stamp 




J ameco 
IMlisUilsUUS 



PHONE 

ORDERS 

WELCOME 

(415) 592-8097 



MAIL ORDER ELECTRONICS - WORLDWIDE 
1021 HOWARD AVENUE. SAN CARLOS. CA 94070 

Advertised Prices Good Thru July 



XR2206IU $14.95 

Function Generator Kit 
lincludes chip, PC 
Boaril antt instructions) 



EXAR 



XR2206KB $19.95 

funclion Generaior t<it 
(includes alt components 
9 C Boarr^ and msimcttons) 



XR-L555 $1.50 

Micro-Power version ol the 
popular 555 Timer and directly 
mtercrianoeable. Dissipates 
1/1 5th ttie power and operates 
down to 2,7 volts Pertect tor 
battery operation and CMOS cir- 
cuits. 



XR2242CP $1.50 

Precision limmg circuit 'or 
generating timing pulses in mi- 
nutes, hours and days or up !o 
1 year by using two Reduces 
cost of time delay circuits. Basic 
555 Timer witti built-in 8-bil 
Counter 



4 40 



XR205 i 8 40 

XR210 

XR215 

XR320 

XRS55 

XR556 

XR567CP 

Xfl567CT 

Xfl1310P 

XR1468Cfi 

XH1438 



XR1489 
XR1800 
XR2206 
XR22Q7 
Xfl220B 
Xfl2209 
XR2211 
XR2212 
XR2240 
XR2264 



KR2556 
)(R2567 
XR3403 
);fi4136 
XR4151 
XH4194 
XR42U,; 
XR4212 
XR4b58 
XR4739 
XH4741 



TYPE 

1N746 
1N751A 
1N752 
IN 753 
1N7M 
tN959 
irt965B 
1N5232 
1N5234 
1N5235 
1N5236 
1N456 
1N45B 
1N4e5A 
tN4001 
1N4002 
1M003 
1N4004 



ZENERS - 

VOLTS W 

3 3 400m 

5 1 400m 

5,6 400m 

6.2 400m 

68 400n 

82 400m 

15 400in 

5,6 500m 

62 500m 

68 500m 

7 5 500m 



■ DIODES — 

PRtCi TYPE 

4 1 00 1N4005 
4:1 00 1H4006 
4'1 00 1N4O07 
4/1 00 1N3600 
IN4148 



RECTIFIERS 

VOLTS W 

600 PIV 1 AMP 
800 PtV 1 AMP 
1000 PIV 1 AMP 
200m 



'1 00 

■1,00 m4305 

28 1N4734 

28 1K4735 ■ 

28 1N4736 

28 1N4738 

■1 00 1N4742 



75 



10m 
10m 



50 PIV 
100 PIV 
200 PIV 
400 PtV 



AMP 

AMP 
AMP 



12 100 1N1185 



12.'1 00 INllSe 



50 PtV 35 AMP 

100 PIV 35 AMP 

ISO PIV 35 AMP 

200 PIV 35 AMP 

■JOO PIV 35 AMP 



SCR AND FW BRIDGE RECTIFIERS 



C36D 
C3eM 
2N2328 
MDA 9KI-1 



5A @ 400V 
600V 
6A @ 300V 
,2A @ 50V 



35A 



MOA 980-3 12A@200V 



CI 0681 

MPSA05 

MPSA06 

TIS97 

TIS98 

IIS133 

TIS135 

40409 

40410 

40673 

2N91S 

2N2219A 

2N2221A 

2fl2222A 

2N2369 

2N236gA 

MPS236g 

2N2484 

2N2906 

JN2907 

2N2925 

MJE2955 

2N3053 



TRANSISTORS 



2N3055 

MaE3055 

2N3392 

2N3398 

PN3567 

PN3568 

PN3569 

MPS3638A 

MPS3702 

2N3704 

MPS3704 

2N3705 

MPS3705 

2N3706 

MPS3706 

2N3707 

2N3711 

2N3724A 

2N3725A 

2N3772 

2N3B23 

2N3903 



5.1 00 
5/1 00 
5/1 00 



2N39D4 
2N3905 
2N390G 
2N4013 
2N4123 
PN4249 
PN4250 
^N4400 
2N4401 
2N4402 
2IM403 
2N4409 
2r«6086 
2N5087 
2^15088 
2M5089 
2N5129 
PN5134 
PN5i38 
2NS139 
2NS210 
2N5449 
2NS951 



3/1.M 
6/1,00 
4/1 00 



5/1 00 
4/1 00 
4/t,00 
4/1 00 



5/t 00 
5'1 00 
5/1 00 



CAPACITOR; 



CORNER 



10-9! 



10 pl 
22 pf 

47 pt 
100 pt 
220 pl 
470 pt 

OOlmt 
0022 

0O47!Ti« 
01 mf 

1/35V 
15/35V 
22/35V 
33/35V 
.47/35V 
,68/35V 
1 0/35V 



100> 
.03 



m^f .05 

0047;iF 05 

04 03 OVF 05 

04 03 022Hf 06 

04 03 047,if 06 

04 ,035 1«F 12 
10Q VOLT MTLAR FILM CAPACITORS 

022mt 

047mf 



10 



.07 



27 



22mt 
+20% WPPED TANTALUMS (SOLID) CAPACITORS 

28 23 17 1 5i3SV 30 26 

28 ■>'■. 17 2 2/2SV 31 27 

28 23 17 3 3/'25V 31 27 

28 ,23 17 4.7/25V .32 28 
28 ,23 17 6e/25V .36 31 

.28 23 17 10/25V 40 35 

28 23 17 15/25V 63 .50 

MMIATUflE ALUMINUM ELECTROLmC CAPAaXOftS 



47/5CV 
1 0/50V 

3 3/50V 

4 7/25V 
10/25V 
10/50V 
22 '25V 
22/50V 
47/2 
47/50V 

100/25V 
10D/50V 
220/25V 
220/50V 
470/25V ■ 

iooo/iev 

2200r16V 



AxiRl LMd 



Ridlil Lwd 



1 0./I6V 
1 0/25V 
1,0/50V 
4 7/1 6V 
4 7/25V 
4 7/50V 
10/16V 
10/25V 
10/50V 
47/50V 
100/16V 
100/25V 
100/50V 
220/1 6V 
470/25V 



Circle 200 on inquiry card. 



BYTE )uly 1978 195 



Whsl s Sew? 



PUBLICATIONS 



Literature Available for Individuals 
Interested in Voltage Control Equipment 



New BITS Catalog Offered 




The new BITS personal computer 
publications catalog is now available 
from BITS, 70 Main St, Peterborough 
NH 03458. The 13 page illustrated 
catalog is a comprehensive listing of 
over TOO personal computing books, all 
evaluated by the editors of BYTE. The 
books cover such topics as: funda- 
mentals for the novice and knowledge- 
able; reference and resource publi- 
cations; the art of computer program- 
ming; programming languages; the 
computer artist and musician; building 
your own computer; fun, games and 
foolishness; and many other areas of 
interest to the personal computer user. 
Write for your free catalog." 

Circle 598 on inquiry card 

Computer Interconnections From 
Hewlett-Packard 

A new application note. Computer 
Interconnections, describes methods by 
which Hewlett-Packard HP 1000 com- 
puter systems and HP 9825 desktop 
computers can be interconnected to 
serve together in a wide range of instru- 
ment control measurement and analysis 
applications. It is available free of 
charge from Hewlett-Packard. The appli- 
cation note, AN 201-6, describes linking 
the two computers via different com- 
munications techniques: HP-IB (Hewlett- 
Packard's implementation of IEEE stan- 
dard 488-1976), RS 232C and an HP 
3070A terminal. Example programs and 
flowcharts depicting program-to-program 
communications for ihe different net- 
works are included. Contact Inquiries 
Manager, Hewlett-Packard, 1507 Page 
Mill Rd, Palo Alto CA 94304.* 

Circle 599 on inquiry card. 



Electrical Engineering Fundamentals 

A Programmed Review for Electrical 
Engineering is a review of electrical 
engineering fundamentals. Its primary 
emphasis is on solving the type of prob- 
lems found on the Professional 
Engineering Examination. Each problem 
has been selected to illustrate a specific 
concept. Background material, in the 
form of tables, formulas, charts and 
graphs, provides all the necessary infor- 
mation to solve the problems. At least 
one solution is given for each problem. 
The book covers all the basic principles 
of electrical engineering. Special con- 
sideration is given to two significant 
areas: the field of digital logic and the 
study of engineering economics. An 
introductory section includes addresses 
of state licensing boards and guidelines 
for exam preparation. An extensive 
bibliography rounds out the volume. 
The book is written by James H Bentley 
and Karen M Hess PhD and is published 
by Van Nostrand Reinhold, 450 W 33rd 
St, New York NY 10001. The price is 
$14.50." 

Circle 600 on inquiry card. 



Hand Portable 10 Channel Printing 
Data Logger Catalog 




A recently published 12 page bro- 
chure describing a high resolution 
printing data logger, Model PDL-10, is 
available from Datel Systems Inc, 1020 
Turnpike St, Canton MA 02021. The 
PDL-10 offers a simple, low cost ap- 
proach to measuring, scanning, and 
logging analog voltages. Ten input 
channels are provided, along with a 
4'/> digit panel meter, a 7 column ther- 
mal printer for instant hard copy print- 
out, scan electronics, and a 99 minutes 
or seconds scan interval clock. Input 
connections are made through con- 
venient rear panel terminals. This color 
brochure details electrical and physical 
parameters, operating instructions, block 
diagrams, application notes, and ordering 
information." 

Circle 601 on inquiry card. 




This 60 page powerstat variable trans- 
former catalog PI 78 consolidates 
descriptive and technical data on the 
complete product line. It gives ratings, 
dimensions, performance curves and 
schematic connection diagrams in an 
easy to read format, and includes metric 
equivalents for universal use and easy 
reference. For a free copy write to the 
Superior Electric Company, 383 Middle 
St, Bristol CT 06010." 

Circle 602 on inquiry card 



New Software Buyer's Guide 

A new publication. Packaged Soft- 
ware Buyer's Guide, is said to include 
44 pages of important software infor- 
mation and can be helpful to any 
businessman who is contemplating pur- 
chasing such a system. 

The guide is reported to give the 
prospective software buyer an in depth 
analysis of the following subjects: how 
to buy a software package for small 
business computers; how to buy a 
general ledger software package; the 
accounts receivable package; the 
accounts payable package; the payroll 
software package; and the inventory 
control package. Price is $15 from MIC, 
140 Barclay Center, Cherry Hill N) 
08034." 

Circle 603 on inquiry card. 



Computer Accessories Catalog 

This catalog contains a wide variety 
of word and data processing supplies and 
equipment including: magetic tapes, 
cassettes, cards, cartridges, floppy disks, 
disk packs, paper tapes, rolls, continuous 
forms, thermal quiet paper, storage 
cabinets, containers, racks, reels, vertical 
format tapes, punches, splicers, auto- 
matic winders and more. Available from 
Computer. Accessories Corp, 21 1 New 
York Av, Huntington NY 11743." 

Circle 604 on inquiry card. 



196 



)uly 1978 ©BYTE Publications Inc 



S-100 

32K STATIC MEMORY BOARD 



features: 

1. FULLY STATIC - usable with all DMA devices. 

2. BUFFERED - with noise suppressed control inputs. 

3. MODULAR - populated in Ik Increments. 

4. RELIABLE - single source +5V regulator 

5. PROM COMPATIBLE - monitors available on request. 

AVAILABLE EITHER IN COMPLETE KITS 
OR ALREADY ASSEMBLED UNITS WHICH 
HAVE BEEN FULLY TESTED AND BURNED IN. 

BARE BOARD $38°° 





KIT 


ASSEMBLED 


8K 


J270OO 


$296'» 


16K 


$440«) 


$465" 


24K 


$580M 


$6120i> 


32K 


$695»» 


$740«' 



niCES QUOTED ARE FOR SOOns MEMORIES 
KITS MID ASSEMBLED UNITS INCLUDE DOCUMENTATION 



DEC* LSI-11 16K MEMORY BOARD 

• QBUS— FULLY "BUFFERED AND 
STATIC NOISE SUPPRESSED 

• MODULAR •PROM COMPATIBLE 

• ADDRESSABLE TO 128K WORDS 

• MAPPABLE IN 4K INCREMENTS 



ASSEMBLED, 

StN $1199'"' 



COMPLETE 

"" $110900 



LAROeST 4 FASTEST STATIC MEMORY AVAILABLE 



SlOO EXPANDABLE MOTHER BOARD 

• 8SL0T EXPANDABLE BACKPUNE— in 
line male and female connectors enable 
backplanes to be plugged together, or the 
female may be used In place of an extender 
board. 
QUIET — ground plane decouples all signal 

lines. 
RELIABLE— SAE 8100 phenolic body, gold 
contact connectors. 



COMPLETE 



$66 



00 



ASSEMBLED 



$8900 



UNIVERSAL "U DESIGN" WIRE WRAP BOARDS 

ALL BOARDS ARE G 10 GLASS EPOXY HAVE Vcc AND GROUND 
PLANES. PUTED THROUGH HOLES, 4 GOLD PLATED EDGE CONNECTORS 



No. 1 BEST ON THE MARKET 
MICRO CPU CARD WITH S ISO 8US. 3 
ON BOARD REGULATORS FITS ALL STAN 
DARD IC SOCKET CONFIGURATIONS 
1700+ HOLES 
SI'E 5 ilO »„„„! 

$23« 



No. 2 

UNIVERSAL BOARD FITS 86 PIN 

SOCKET mlH 10' CONTACT 

SPACING MADE BY LEADING COM 

PUTER MANUFACTURER AS IN HOUSE' 

BOARD 1600+ HOLES 

SIZE 4 7/8 <;S/8' 57'' 



SlOO EHENDER BOARD 

wilh connector 

A MUST for trouble- , 1 1 7 95 

shooting your Computer boards * A / 



BUILD YOUR OWN 

LOGIC PROBE 



24 TO-92, SMALL SIGNAL DARLINGIONS » • qi: 
AND 24 LEDS.-ALL FUNCTIONAL only ^4' 



MAXI SWITCH KEYBOARDS 

UNENCODED MOUNTED ON GIG 6USS EPOXY BOARDSA BUCK 
METAL FRAME KEEPS KEY SWITCHES SECURELY IN PLACE. 



No. 1 

-53 key main keyboard 
-10 auxiliary & cursor control keys 
-11 key numeric pad 
Bank of 5 auxiliary power and 
control, rocker arm switches 
one of them lights up. 

$3995 

WIRE WRAP SOCKET CONNECTOR 
FOR NO. 1 KEYBOARD $295 



BUILD YOUR OWN 

PAPER TAPE 
READER 

l/IO" CENTER STACKABLE 

PHOTO 
TRANSISTORS 

10/$96o 



GOLD WIRE WRAP 
SOCKET STRIPS 



MAKE UNIVERSAL 
END AND SIDE 

STACKABLE WIRE 
WRAP BOARDS 

12 PIN„ 

3 LEVEL 48C 

14 PIN,„ 

2 LEVEl 4gC 

3 LEVEL 56c 



7 PIN STRIP 
TOP VIEW 




No. 2 

'53 key keyboard 

1 auxiliary power/control 

DPDT rocker arm switch 

$29" 

BEIGE METAL FRAME MOUNT FOR 
NO. 2 KEYBOARD $995 



SOCKET CONNECTOR FOR 
NO. 2 KEYBOARD 



$29 



TTL COMPATIBLE 
REED RELAY 

400 OHMS 
$149 7/$975 



OUR NEW 
ASCII KEYBOARD 

HAS ON BOARD UV PROM, A MAIN 
KEYBOARD SECTION OF 58 KEYS, A 
HEX PAD OF 15 KEYS AND 16 MORE 
PERIPHERAL KEYS. 89 KEYS TOTAL & 
ASCII ENCODED for only $99" 



POWER SUPPLY PARTS 



DIODES 



EDGE VIEW METER 

CHARGE DISCHARGE SCALE READS 20.0,40 
MOVEMENT -1-60, I20mA «'OAQ 

135 OHMS ■^i.*^ 



4K STATIC RAMS 



2114 650ns 
TMS40454 450ns 
HM 472114 300ns 



600m« J6.25 
300nm SIO 95 
200mw $11 95 



l.a SOCKETS 

LOW PROFILE-SOLDERTAIL 



8 PIN 

14 PIN 

16 PIN 

22 PIN 

24 PIN 

28 PIN 

40 PIN 



GOLD 

INLAID 

10/11,59 

10/11,89 
10/J1,99 
5/$l,69 
5/$l,89 
5/J1-99 
4/Jl,99 



TIN 

10/$1,35 
10/11,49 
10/11,59 
5/Jl,49 
5/tl,59 
5/H,69 
4/$l,69 



MINIATURE 

16 BUnON PADS 

4i4 MATRIX ENCODED «> -I 05 



$is 



lor that pmlessioral loach CARBIDE DMU. Rin 
For P.C BMIID WORK 

ASSORTMENT OF SIZES FROM NO, 55 TO NO, 70 

5MIX/J7« 10MIX/$12«9 lOOMIX/JSS" 



IN4001 50V al lA 
IN4003 200V al lA 
IN4007 lOOOV al lA 
IN250 GOV al 20A 
IN3909 50V al 30A 




6c 
8c 
12c 
95c 
J1,Z5 


BRIDGES 






FAST RECOVERY AVALANCHE BRIDGE 
IN4436.T 200V al lOA 
FULL WAVE MINI BRIDGE' WITH TAB 
PR lOE lOOV al 12A 


J425 
TERMINALS 
$3 75 


5% ZENERS 






IN4733A 5 1V 1« 
IN4739A 9 1V 1» 
IN4744A 15V 1» 




39c 
39c 
39c 


VOLTAGE REGUUTORS 

UA723 VARIABLE 2V to 3 7V 
78L05 5V at lOOmA TO 92 
340T 6 6V at 1 AMP TO 220 


PWSIIC 
38c 


MEIAL 

69 c 
3/98C 
2;98c 


PASS nANSISTORS 






MIE3055 lOA PLASTIC 
2N3055 lOA TO 3 
2N5301 30A TO 3 




89c 

95c 

Jl 95 


PROTECT YOURSELF, INSTALL AN ELECTRONIC 
CROWBAR CIRCUIT IN YOUR POWER SUPPLY 
CROWBAR SCR C220O 400V at lOA 


SI 75 



OPTO DEVICES 



PHOTO 
TRANSISTORS 

SIMILAR TO FPT 100 

4/98c 

PHOTO 
DARUNGTONS 

MOTOROLA 

4/98c 



ULTRA 
HIGH 

SPEED 

PHOTO 
DETECTOR 

5ns 
RISE TIME 

$3's 



EXIREMELY 

SENSITIVE 

IIGHI ACTIVATED 

SCR 

t'lggeoble by 

flashlight at 
several tiun 
(Jred yards 

$2» 



INFRA RED 
DETECTOR 

ULTRA LOW LEVEL 
PIV 7V 



I ma 



$495 



HEWLETT-PACKARD 

JUMBO-RED 

HIGH EFFICIENCY 



OH BOARD 
SUIUS 

INDICAIOI 



LED 



6/$l»o 



SOUR CELLS 

2ii2cm I30ma 

$1" ea. 10/$99(i 



LED LAMP 

EXTREME WIDE ANGLE VIEWING 

3/98C 10/$2«5 



GOLD 



EDGE CARD CONNECTORS 



No. 1 
SAC185/2 2 

SINGLE ROW, IS 
PIN CONNECTOR 
WITH 156" CON 
TACT SPACING 



99c i 



No. 2 

SAC22S/2 2 

SINGLE ROW, 22 
PIN CONNECTOR 
WITH 156 CON 
TACT SPACING 



99c i 



No. 3 
2VH31/ICB6 

31 SOLDER LUG 
CONNECTOR WITH 
125- CONTACT 
SPACING 

99c 



HIGH VOLTAGE DIODES 

EPOXY 1500V at 1 AMP 10/Jl 99 

EG250 2500V at 350mA 95c 

HV60EL 6KV at 25iiiA $1 95 

SUBMINIATURE 20KV at 100mA S2 95 



3-1/2 DIGIT LCD.'s 

LIQUID CRYSTAL DISPLAY 



No. 1 

4' CHARACTER 

WITH CONI^ECTOR 



$6 



95 



No 2 

IMIS MiNIAIUFtI I C D 
IS IDfAl FOB POCKEl 
SI?EO INSIRIIMIMS 



$395 



WIRE WRAP 
POST 

? LEVEL 

10 98c 
100 17 40 

I000'J64 00 
3 LEVEL 
10 Jl 25 
100 $8 60 

!000'$7? 00 



HI-REL GOLD 

WIRE WRAP 
SOCKET PIN 

10/51" 

1000/$79«> 

LIST PRICE 29c 



OP AMPS 

SINGLE 

709 II 

741 1: 

DUAL 

MC1458 

QUAD 

LM3900 



39c 



49c 



DIODES 

IN9I 

IN270 

IN914 

IN3600 

IN4148 



15c 
12c 
15c 
15c 
lOc 



TMNSISTORS 

2N2222 12c 

2N3904 12c 

2N3906 12c 

2N3053 49c 



D/A 
CONVERTER 

SIGNETICS 
NE5008 

$9« 



SUB MINIAIURE 

CRYSTAL 
FILHR 

455 KHZ 

WITH DAIA 



$295 



NO BACK ORDERS FREE DELIVERY BY UPS <"< ^s orders only 

YOUR PARTS OR IMMEDIATE REFUND OR OY SURFACE MAIL, IF SPECIFIED — CALIF, RES ADD 6% SALES TAX 

MONEY BACK GUARANTEE (mds and led devices excluded, $20 MINIMUM 

FOR UNDER 8 HOUR PROCESSING SEND MONEY ORDER, CERTIFIED OR CASHIERS CHECK, 
SORRY' WE CANNOT ACCEPT PURCHASE ORDERS. CODS, PHONE ORDERS OR CREDIT CARDS 



FOREIGN ORDERS 

CANADA PUFRIO RICO U S 
possessions add us $3 M AIL 
OTHER ADD U S t' 00 

IMMEDIATE SHIPPING ON CHASE 
MANHATTAN FIRST CITI2ENS 
CASHIFRS CHECKS S CANADIAN 
POSTAL MONEY ORDERS 



LEDS 

YELLOW. 
GREEN. OR 

AMBER 

(SPECIFY COLOR) 

3/88C 



LOS ANGELES 
(213) 967 46)1 

LMN ELECTRONICS 

1042 E GARVEY AV, W COVINA CA 

(VINCENT & SAN BERDO FWY ) 

tUE -^ SAT 10 fl - ClOSID SUN i MON 



DROP INTO ONE OF OUR LOCATIONS 

PORTLAND 

1503) 646 4044 

WIZARD OF PARTS 

8225 SW CIRRUS Dfi BEAVEfiTON ORE 
(KOU BUS CNTR WASHINGTON SQUARE) 



F. Reichert Sales 

1110 E. GARVEY AVE. 
W. COVINA, CA. 91790 



DENVER 

1303) 573 5214 

ELECTRONIC LOLLIPOP 

5643 N BROADWAY DENVER, CO 
il2S & SSIh AVE ) 



ALL ITtMS SUIIECT TO PRIOR SALE 

Circle 207 on inquiry card. 



PRICES SUBJECT TO CHAmE 
BYTE July 1978 197 



Circle 247 on inquiry card. 



CLjbBrc[m boards 



MB-1 MK-8 Computer RAM (not S-100), 4KX8 uses 
2102 type RAMs. PCBD only $22.00 

MB-3 1702A EROM Board, 4KX8, S-100 swilchable 

address and wait cycles, kit less PROMS $58.00 

MB-4 Basic 4KX8 ram, uses 2102 type rams S-100 

buss. PC board $24.96 

MB-6A Basic 8KX8 ram uses 2102 type rams, S-10Q 

buss, PCBD $24.95 

MB-7 16KX8, Static RAM uses uP410 Protection, 

fully buffered. KIT $375.00 

MB-8A 2708 EROM Board, S-100. 8KX8 or 16KX8 
kit without PROMS $75.00 

MB-9 4KX8 RAM/PROt^ Board uses 2112 RAMS or 
82S129 PROM kit without RAMs or PROMs ,$72.00 
10-2 S-100 8 bit parallel I/O port, % of boards is for 

kludging. Kit $46,00 PCBD $24,95 

10-4 Two serial I/O ports with full handshaking 
20/60 ma current loop: Two parallel I/O ports. 

Kit $130. PCBD $24.95 

VB-1B 64 X 16 video board, upper lower case Greek, 
composite and parallel video with software, S-100, 

Kit $125.00 PCBD $24.95 

Altair Compatible Mother Board, 11 x 11 '72 x Vb". 
Board only . $40.00. With 15 connectors . $90.00 

Extended Board full size. Board only $ 9.00 

With connector $13.00 

SP-1 Synthesizer Board S-100 

New Low Price Kit $135.95 



82823 


$1.50 


PRIME 


DEVICES 


823123 


1.50 






82S126 


1.95 


8080A 


$11.50 


82S129 


1.95 


8212 


3.75 


828130 


3.00 


8214 


6.50 


82S131 


3.00 


8216 


3.95 


MMI6330 


1.50 


8224 


4.00 


4N26 


.75 


8228 


6.95 


4N27 


.75 


8251 


9.95 


4N2E 


.75 


8255 


9.95 


LM323 


2,96 


21L14 


8.50 



/YfTnC /inc. WAMECO INC. 

MEM-1 BKXB fully buffered, S-100, uses 2102 type 

rams, PCBD $24.95 

Mather Board 12 slot, terminated, S-100, board 

only $30.95 

CPU-1 8080A Processor board S-100 with 6 level 

vector interrupt PCBD $24.95 

RTC-1 Realtime clock board. Two independent in- 
terrupts. Software programmable. PCBD ..$23.95 

EPM-1 1702A 4K Eprom card PCBD $24.95 

EPM-2 2708/2716 16K/32K 

EPROM CARD PCBD ...$24.95 

SHORT MOTHER BOARD Short Version of QM-IA 

8 Slots PCBD $25.95 

2102AL-2 Prime 260 NSEC $1.70 

2102AL-4 Prime 450 NSEC $1,30 

2708 Prime (National) $10.00 

1702A-6 AMD Prime , $3 50 

1702A Intel Not Prime (2US) $2.00 

2501 B $1.50 1488N $1.50 

2502B 1.50 1489N 1.25 

2504 1.50 MC4044 2.25 

2507V 1.60 8038 3.90 

2510A 1.50 5320 5.95 

2517V 1.50 5554 1,90 

2518B 1.50 5555 2.50 

251 9B 1,50 5556 2,50 

2621 1,50 6055 1,25 

2522 1,60 5312 4,00 

2525 1,50 MH0026 1,50 

2527 1.50 MH0026 1.75 

2532V 1.50 MH0028 1.90 

2529 2.75 5262 .50 

2533V 1.95 2101 3.50 



m 




419 Portofino Drive 
San Carlos, California 94070 

Please send tor IC, Xistor 
and Computer parts list 



MIKOS PARTS ASSORTMENTS 

All piece parts for assembly of Wameco and 8SM 
PCBD's. All Factory Marketed Parts. Order PCBDs 
right. 

Mikos #1 Parts for MEM-1 PCBD with prime 

2102AL-4 450 nsec rams. Less PCBD $105,00 

Mikos #2 Parts for CPU-1 PCBD with prime 8080A 

8212's and 8214, Less PCBD $62.00 

Mikos #3 Parts for MEM-1 PCBD with prime 

2102AL-2 250 nsec rams. Less PCBD $128.00 

Mikos #4 Parts for QM-IA with super low loss gold 

plated connectors. Less PCBD $52.00 

Mikos #5 Parts for RTC-1. Less PCBD $40.00 

Mikos #6 Parts for VB-1B less molex connectors 
and PCBD $65.00 



82S06 


$1.00 


8T26 


$2.00 


82S07 


1.00 


8T28 


2.00 


828 50 


1.00 


8T34 


2.50 


82S62 


1.00 


8T37 


250 


75324 


1,50 


8T38 


2.50 


75325 


1.50 


8T74 


1.50 


8T01 


2.50 


eT80 


2.50 


8T09 


1.25 


8T90 


2.50 


8T10 


2.50 


8T95 


2.30 


8T13 


2.50 


8T96 


2.45 


8T14 


2.50 


8T97 


1.50 


8T20 


2.50 


8T98 


2.00 


8T23 


3.00 


8T110 


2,00 


8T24 


2.50 


567 


1.50 



Check or money order only. If you are not a reg- 
ular customer and your order is large please 
send eitlier a cashier's check or a postal mon- 
ey order, otherwise there will be a delay of two 
weeks for the check to clear. All items post paid 
in the U.S. Calif, residents add 6% tax. Money 
back 30 day guarantee. We cannot accept re- 
turned IC's that have been soldered to. Prices 
subject to change without notice. $10 minimum 
order. $1.00 service charge on orders less 
than $10. 



COMMERCIAL GRADE EQUIPMENT- HOBBYIST PRICES!! 





TAPE DRIVES 



MODEMS AND 
PHONE COUPLERS 



lAMPEX MODEL TMX TAPE DRIVES with built-in NRZl formatter. 806 
BPI, 9 track, 12 IPS, 8" reel includes 8 bit CPU controller diagram and 8080 
interface instructions. Ideal for microcomputerist who wants back-up mass 
storage and access to IBM-tvDe svstems via standardized W mag tape. . .3750 
•AMCOMP SERIES 2700 TAPE DRIVES: current model, vacuum column 
control; like new: 

(2) MODEL 2749 - 45 ips, 800 BPI, 7-Track, 10" reel $1500 

(3) MODEL 2769 - 125 ips, 800/1600 BPI, 9-Track, 10" reel. . .$3000 
•TAPE DRIVE FORMATTERS, "Pertec Standard Interface": 

(3) AMCOMP SERIES 2900 NRZl/Phase Encoded, 25-125 ips.. 01500 
(1) PICO MODEL 1011, NRZl, 800 BPI FORMATTER/ 

CONTROLLER for PDP-1 1 $2000 

MODEMS, Full-Duplex, Auto Answer circuitry, by VADIC CORP. 

BELL 103 Type (300 Baud) Circuit Card only $75 

BELL 103 Circuit Card, Power Supply, Case, Connectors $125 

BELL 202 Type (1200 Baud) with Reverse Channel Transmission from $125 

DB-25 MALE CONNECTOR + 2 wire cable to Phone Jack $4 

PAPER TAPE READER (ADDMASTER 601-1): 150 cps, LED sensors read 
5-8 level tapes, bi-directional stepper njotor, includes TTL serial interface 

plus 8080 parallel interface instructions. Requires -i-5V & 24V $90 

DATATEST PROGRAMMABLE AUTOMATIC CIRCUIT CARD ANALYZER 

MODEL 4000A S2000 

MODEL 4700 $6000 

DIABLO SVSTEMS Spare Circuit Cards for HyType Printer, Series 20 h- 40 

Disk Drives; complete but defective or below current revision level , $20 

ASai ENCODED KEYBOARD from HyType Termmal, never used $60 

TELEPHONE ACOUSTIC COUPLER $30 




SELECTRIC TERMINALS 



• SELECTRIC I/O TERMINALS (by GTE/INFORMATION SYSTEMS). In' 
eludes 8080 interface plus software ASCII translation and I/O driver routines 
15" carriage, interchangeable type spheres & carbon/fabric ribbons. Built-in 
modem optional, 

MODEL 5541 (IBM Corresoondence Code. 2741-tvDe terminal) $895 

MODEL 5550 (Corres. Code w/350 char, line buffer memory + built-in 
cassette drive for data storage/off-Mne printing/word processing. . '.$1495 
MODEL 5560 (ASCII Code, with cassette tape drive) $1495 

• IBM SELECTRIC TYPEWRITER with magnets, switches & magnet driver PCB 
(from GTE/IS Terminal) plus instructions for 8080 printer/driver interface. 

Typewriter mechanism complete, cleaned & adiusted $325 

Aluminum Case & Power Supply (-I-24V, ±12V, +5V («' 5V) S75 

• CONVERT IBM OFFICE SELECTRIC to I/O Typewriter; solenoids, switches, 
wire harness, magnet driver PCB plus instructions + 8080 Interface Diaa. $150 

• IBM PIN-FEED PLATENS for 15" SELECTRICS (13 1/8 pin-to-pin) new $50 

• IBM SELECTRIC APL TYPE SPHERES (Specify EBCDic or Correspondence 
Code), new $15 

• FORMS TRACTORS, Moore Variable-width "Form-A-Liner" new $50 

for 15" Carriage IBM SELECTRICS used $30 

■ DIGITAL CASSETTE DRIVE (from GTE/IS Terminal) 2400 baud, FWD/ 
REWIND/STOP circuitry, plus tape head, but no read/write electronics. . .$25 

■ INTERDATA 8-BIT MINICOMPUTER (Model One), includes full front panel, 
4K core memory (16K addressable), plug-in teletype port; optional serial I/O 
+ Tape Drive Controller PCB's. software $300 

■ RIBBON CABLE 50 Strand X 4' long terminated with 3M edge connector 
(.10" spacing) + paddle card $3 

• AC LINE FILTER 10AMP RFI (110/230V) with Line Relay + Fuses new$15 



Call or write for details, quantity discounts, order 
forms, AH orders shipped from stock — no back orders, 
no substitutions. All equipment is shipped insured 
FOB Palo Alto vuithin 7 days after check clears or COD 
jprder is received. M/C & VISA cards accepted. 



PACIFIC OFFICE SYSTEMS, IXC. 

2600 EL CAAIIXO REAL. SUITE 502 

PALO ALTO. CAIJF. 94306 



Tel: (415) 321 - 3866 



90 day warranty against defects in material or work- 
manship on all used equipment. Full documentation 
included PLUS interface instructions where indicated. 
Availability subject to prior sale. Prices may change 
without notice. 






198 BYTE luly 1978 



Circle 296 on inquiry cartd. 



Close-out Purchase by MiniMicroMart 

Save up to 50% 

on the famous TDL SMB 
System Monitor Board 









iiu!iua»uiiiiiiiTmTWHmiTmimiii»iiii 



TWO SERIAL PORTS, PARALLEL PORT, MONITOR ROM, 2K OF RAM, 

AND CASSETTE INTERFACE ON ONE BOARD. FEATURE ARTICLE IN APRIL BYTE 



AVAILABLE BARE BOARD, PARTIAL KIT, COMPLETE KIT, OR ASSEMBLED AND TESTED - 

SMB Bare Board w/const, manual . 05-1002-0 $ 49.95 
SMB Board, all IC sockets, addressing and buffering 
components, ppwer-on jump circuits and 



FEATURES 

Does power-on jump to monitor 

Two fully programmable serial ports (1 10 to 9600 baud 
RS232or20-milloop) 

Programmable 8-bit I/O port 

Provision for 1200-baud audio cassette interface 

Provision for 1 K or 2K on-board static RAM 

Provision for 2K ROM (TDL Zapple Monitor or, with 
minor changes, one 2708 or 2716 EPROM) 



support circuitry for ROM/RAMs 05-2002-1 99.50 
SMB Board, same as above but incl. all components 

for one parallel/one serial interface05-2002-2 1 1 9.50 
SMB Complete Kit, incl. parallel port, two serial 

ports, audio cassette interface . . 05-3002-0 147.50 

SMB Assembled and Tested 05-4002-0 1 97.50 

Zapple Monitor ROM for above .... 05-9002-0 29.95 

IK RAM (two EMM 4148's) for above 05-6002-0 29.95 
Add $2.00 for shipping and insurance. 



RAMS/EPROMS 

Prime 2708 EPROMs 
full spec, 450ns 

$9.95 each 

EM M4200 4K Static RAMs 
$10.95 each 

T. . 4K Static RAMs 

4Kx1 TMS4044's 

(as usecJ in Heath boarcis) 

$8.98 each 

1Kx4TMS4045's 

$9.89 each 

4Kx1 TMS4027-25's (16-pin) 

$3.95 each 


CLOSE-OUT 
SPECIALS 

S-100 16K Static RAM Boards 

for EMM 4200's (bare boards) 

$24.95 

S-100 1702 EPROM board 

(holds 8 PROMs) complete kit 

$49.95 

S-1 00 4K Static RAM Board 

Kit(less2102's) 

$19.95 


ASCII 
Keyboards 

Used surplus 

Excellent condition 

Control functions 

Upper/lowercase 

Ready to use 

$49.95 


Teletypes (used) 

- IMMEDIATE DELIVERY - 

KSR-33's from $495.00 
ASR-33's from $695.00 


CONTACT US FOR 

ADD-ON MEMORY 

FOR TRS-80 


LOTS OF OTHERS 

Write for close-out and surplus catalog 
for fantastic prices on TV Typewriter III 
boards and kits, cursor boards, screen- 
read boards for above (can also be used 
with SWTP CT-1024); also, 25 x 40 
video boards, UART boards, and 
Baudot-to-ASCII conversion boards. 


S-100 Prototype Boards 

General-Purpose 

$18.95 

Wire-Wrap Version 
$19.95 


IBM 735 I/O 
Selectrics (used) 

from $395.00 



MiniMicroMart, Inc. 



Circle 251 on inquiry card. 



1618 James Street, Syracuse NY 13203 
Phone (315)422-4467 

BYTE luly 1978 199 



Whafs New? 



SYSTEMS 



Microprocessor Card for S-100 Bus 



INFO 2000 Disk System Upgrades 
Heatiil<it H8 to Z-80 




A complete dlsl< system for tlie 
Heathl<lt H8 lias been announced by the 
INFO 2000 Corporation, 20630 S 
Leapwood Av, Carson CA 90746. The 
INFO 2000 Disk System is designed to 
upgrade the 8080 computer to a Z-80 
system by replacing the Heathkit 8080 
processor board with the INFO 2000 



Z-80 disk adapter board. The complete 
disk system for the H8 computer in- 
cludes PerSci dual diskette drives, power 
supply, case, intelligent controller, 
adapter, cables and disk monitor in eras- 
able read only memory. The adapter 
board contains the Z-80 microprocessor 
and all support chips, 7 K of erasable 
read only memory, 1 K of scratchpad 
programmable memory for the disk 
monitor, and all necessary logic for inter- 
facing the disk system to the Heathkit 
H8. With the addition of the system and 
installation of its adapter board, the H8 
computer can operate in either of two 
switch selectable modes. One mode en- 
ables continued use of the H8 erasable 
read only memory monitor with the ex- 
isting Benton Harbor software. The sec- 
ond mode supports the disk monitor, 
and other software adapted to the sys- 
tem for use with all their disk systems. 
Cost for the complete system is $2750 
with a 90 day warranty. A 5% discount 
is offered when payment in full accom- 
panies order." 

Circle 634 on inquirv card. 




Microcomputer System Features 
Dual Disk Drives 




The GNAT-PAC System 9 which in- 
tegrates the GNAT microcomputer sys- 
tem with dual standard floppy disk 
drives is now available. With disk storage 
of up to 1 million bytes, the System 9 is 



intended for use in small business appli- 
cations, communications, or process con- 
trol. The standard computer hardware 
includes the 8080A processor, 32 K 
bytes of programmable memory, 16 K 
bytes of read only memory with 2 K 
bytes of programmable read only mem- 
ory, 4 RS-232 serial lO ports, and floppy 
disk controller. Dual disk drives provide 
500 K bytes of disk storage per drive. 
The System 9 is packaged in a 10'/2 inch 
high cabinet (26.67 cm) and includes 
card rack, fan, 11 slot mother board, 
RFI line filter, wiring and power supply. 
Software includes a monitor, loader, 
disk operating system with assembler, 
editor and dynamic debugger. FOR- 
TRAN, BASIC and other high level 
languages are available. Price is $5500 
from GNAT Computers Inc, 7895 Con- 
voy Ct, Unit 6, San Diego CA 921 11." 

Circle 635 on inquiry card. 



The 6800-CPU microprocessor card 
for the S-100 bus brings all the ad- 
vantages of the 6800's architecture to 
the S-100 user. The software support for 
the 6800 is now available to the S-100 
bus user. For the small business user or 
personal computer user, this micro- 
processor card provides full turnkey 
operation and maximum system com- 
patibility as well as an RS-232 20 mA 
interface (bps rate selectable with a 
DIP switch), paper tape reader control. 
Motorola MIKBUG read only memory 
operating system, power on reset, on 
board dynamic memory refresh, slow 
memory interfacing and three state data, 
address, and control lines. Prices are 
$179 in kit form and $269 assembled, 
burned in and tested. Contact 
Datatronics, 208 E Olive, Lamar CO 
81052.» 

Circle 637 on inquiry card. 



Single Board Microcomputer Holds 8 K 
PROM plus 8 K Volatile Memory 




The Little Brain I is a microcomputer 
using the 6802 processor mounted on an 



S-100 board which includes as much as 
8 K words of ultraviolet erasable read 
only memory and 8 K words of fully 
static programmable memory plus an 
RS-232C channel on a single board. The 
Little Brain I has on-board voltage regu- 
lators, fully buffered address, data and 
control buses along with a 128 word 
scratchpad memory. Custom program- 
ming services are available. The fully 
socketed version with a 2 K monitor and 
debug program and 1 K words of pro- 
grammable memory sells for $395 and is 
backed with a one year warranty. Con- 
tact BPI Electronics, 4470 SW 74th Av, 
Miami FL 33155." 

Circle 636 on inquiry card. 



Ohio Scientific Catalog 

Now available from Ohio Scientific 
is a 1 9 page illustrated catalog detailing 
a full line of computers, software and 
hardware for personal and business use. 
Prices range from $298 for their C2-0 
Model 500 which is a complete com- 
puter on a board featuring standard 8 K 
BASIC in read only memory, 6502 
microprocessor, 4 K of programmable 
memory and a serial port up to $3590 
for the C3-S1 Challenger 111 System 
with dual drive floppy, 32 K program- 
mable memory, serial port, cabinets and 
power supplies. For this free catalog 
write Ohio Scientific, 1333 S Chillicothe 
Rd, Aurora OH 44202." 

Circle 638 on inquiry card. 



200 



luly 1978 ©BYTE Publicilions Inc 



FREE PROBES FREE PROBES FREE PROBES 




ILM3A 3 dig 1% DC $125. 

IlMS.SA ZVi dig .5% DC $147. 

IlM40A 4 dig .1 % DC $190. 

|lM4A 4 dig .03% DC $227 

Rechargeable batteries and charger in- 
cluded 

Measures DC Volts, AC Volts, Ohms and 

Current 

Automatic polarity, decimal and overload 

indication 
> Rechargeable batteries and charger 
I* Measures DC Volts, AC Volts, Ohms and 

Current 
I* Automatic polarity, decimal and overload 
I indication 
I* No zero oNJjustment and no full-scale ohms 

adjust 

• Battery-operated ~ NiCad batteries; also AC 
line operation. 

• Large LED display tor easy reading without 
interpolation 

■ Sizs: 1.9'Mk2.7'Wk4"0 
Parta & iftbor guwanlvad l yav 
Tilt ataod option % *.» 

• Laathwcase 




S-100 BUS EDGE CONNECTORS Of* 



M5-15 MINISCOPE 



ft»cntig—blw Btlfft A Ctingv Unit 



15 megahertz bandwidth. 

External and Internal trigger. 

Time base — ,1 mlcrosec 10 0.5 Sec/dli 

sellings •3%. 

Battery or line operaiion 

Automaric & line sync modes 

Power consumclion < 15 watls. 



Ilinga i 1% 



11 



PROBE 1« 

PROBE IC Mith the 

pufchaseo' SCOPE 

and the MENTION ol 

this MAGAZINE 






> MS-21S Dual Trace Version of MS-1S S39S.00 ^ 
3 LEVEL GOLD WIRE WRAP SOCKETS 




SIOO-WWG 50/100 Cent. 1 26 ctrs 
3 LEVEL WIRE WRAP 025' sq posts 
on 250 spaced rows. GOLD plated 

1-4 59 10-24 

$4.00 $3.75 $360 



S100-STG 50/100 Cont 125 ctrs 
DIP SOLDER TAIL on 250 spaced 
rows for VECTOR and IMASI 

motherboards GOLD plated. 

1-4 5-9 1024 

$4.00 $3.75 $3.50 



RG81G 50/100 Com. ,125 ctrs. DIP 
SOLDERTAILon 140 spaced rows for 
ALTAIR motherboards GOLD plated. 
$6.00 



S 1 00 -WWN 50/100 Com 125ctrs 
3 LEVEL WIRE WRAP 025' sq posts 
on 250 spaced rows NASGLO tin 
nickel plated 

14 59 10 24 

S3 50 $3 25 S3 00 



SIOO-STN 50'100Cont 126 ctrs 
DIP SOLDER TAIL on 260 spaced 
rows for VECTOR and trvlASI 
motherboards NASGLO tin-nickel 
plated. 

14 69 1024 

$3 60 $3 25 $300 



R681-3 60/100 Com 125 ctrs 
PIERCED SOLDER EYELET tails 
GOLD 
S7 35 



Other Popular Edge Connectors 



R644-3 22/44 Cont 
WRAP tails GOLD 
$471 



166 ctrs WIRE 




r^rr special 

^^r^^y^^^^AACS2 100 for •14"" 
- ■ 16CS2 100forM6" 

14plnCS2 t0lor'2" 
16plnCS2 8lor*2" 
These low cost DIP sockets mil accept 
both standard width plugs and chips. 
Foi use witri chips, the sockets offer a lOw 
pfoliie height of only 125" above the board. 



WRAP POST 

for 042 dia. holes 

(all boards on this page) 
T-44pkg 100 S 2.U 
T-44 pkg 

1000 S14.00 

A-13 hanflinslallmg 

tool S Z.BO 



XX)3] A Woodley A^o Sepulveda CAo 91343 

TermS( ViSA. MC. BAC check. Money Order. C D . U S Funds Only LA residents add 6% sales tax Mini- 
mum orQp $10 00 Orders less than $7b 00 include 10% shipping and hjndlmg. excess refunded. Just in case 
please'inciude your phone no "Sorry.no over the counter soles" Good thru Aug15. 1978 

phone orders welcome (213) 893-8202 oEuanc 



ir latest brochure. 



lonal inquiries 




3/ $1.00 
An / tin nn 



FREE PROBES FREE PROBES FREE PROBES 



Circle 304 on inquiry card. 



BYTE luly 1978 201 



Whsfs New? 



2708 and 2716 EROM Programmer 
for KIM-I 



Light Pen Literature Available 




A new model LP-316 super high sen- 
sitivity light pen for long or different 
focal distances has been introduced by 
Information Control Corp, 9610 
Bellanca Av, Los Angeles CA 90045. 
The pen features a finder beam to locate 
the target, and patented touch sense acti- 
vation to allow the pen to be held back 
away from the screen for better visi- 
bility. Luminous sensitivity can be ad- 
justed down to 0.5 footlamberts. The 
LP-316 carries a full year warranty. For 
more information and a complete 
catalog of ICC light pens, contact the 
company." 

Circle 645 on inquiry card. 



Wide Applications for New 30 MHz 
Dual Trace Scope 




The LBO-520 oscilloscope is a 30 
MHz dual trace instrument with a fixed 
delay line. According to the manufac- 



turer, it has been designed for applica- 
tions requiring high accuracy signal 
viewing, single shot trigger, built-in delay 
and high sensitivity. It is further re- 
ported that the unit has 5 mV sensitivity 
to facilitate accurate signal viewing from 
video cameras and other low level 
sources. The instrument's 1 shot trigger, 
on both channels, assures instant capture 
of transient phenomena without guess- 
work or double takes. A 20 ns per cm 
sweep capability combined with a rise 
time of 1 1.7 ns lets the observer view the 
fastest signals in typical small computer 
systems with ease. The 120 ns built-in 
delay line permits easy viewing of the 
leading edge of a pulse or pulse train for 
quick determination of signal character- 
istics. Contact Leader Instruments Corp, 
151 Dupont St, Plainview NY 11803." 

Circle 646 on inquiry card. 



Single Sided Wire Wrap Boards 
in Metric Sizes 




Single sided integrated circuit plug- 
gable wire wrap boards are available in 



metric dimensions from Garry Manufac- 
turing Company, 1010 Jersey Av, New 
Brunswick NJ 08902. Both single sizes 
(series SMP64) and double sizes (series 
DMP64) are included in the new line. 
The SMP64 accommodates 20 16 posi- 
tion integrated circuit chips while the 
DMP64 size will accept 55 16 position 
integrated circuit chips. The boards are 
supplied with either 16 position molded 
sockets or 16 position patterns of indi- 
vidual socket/terminals for maximum 
heat dissipation. They are designed to 
provide wire wrapping terminals on the 
component side, allowing the wire wrap 
boards to be spaced interchangeably 
with standard printed circuit board rack 
assemblies. The boards are supplied with 
or without a 64 position right angle lO 
connector (Garry P/N MPS64-PD). They 
are available at prices ranging from $2 
to $3 per integrated circuit socket 
position." 

Circle 647 on inquiry card. 



^m 

KM 
tern 

cai 

KM 
KM 

K3I 




1 
11 

'4 


EM 

trm 
■m 

KM 


■M-'--i2m:-^' 


3 


^^^B>'to U 



Optimal Technology Inc, Blue Wood 
127, Earlysville VA 22936, announces 
a programmable read only memory 
programmer for the KIM-1 microcom- 
puter with provisions for programming 
both the 2708 and 2716 (5 V only) 
EROMs. By using the KIM-1 monitor, 
any programmable memory starting 
address may be specified up to 65 K. 
Additionally, any starting address within 
the address space of the programmable 
read only memory may be specified 
along with the number of bytes to be 
programmed. The programmer has a 
verify mode which confirms that all bits 
have been programmed correctly. Com- 
pletely assembled and tested, the pro- 
grammer is packaged on a single printed 
circuit board and the connector is fur- 
nished. The program will run on all 
computers which utilize the MOS 
Technology 6S0X microcomputer. One 
and a half lO ports are required. Price 
is $59.95." 

Circle 648 on inquiry card. 



New Soldering Flux 

The flux is called Spec-Master and is 
available as a liquid, cored solder, paste 
solder and soldering paste. It is intended 
for use where a perfectly clean and safe 
residue is necessary after only a mild 
water wash. According to the company, 
the flux is available in strengths strong 
enough to solder stainless steel yet safe 
enough to yield electronically clean sur- 
faces after water washing. It is said to be 
nonflammable, nontoxic, nonirritating 
and nonfuming. For further information 
write: Nokorode Soldering Products 
Division, M W Dunton Company, POB 
6205, Providence Rl 02940." 

Circle 649 on inquiry card. 



202 luly 19780BYTE Publicilions Inc 



POLY 
PAKS 



PACTS wccrsucp 

POLY PAKS INTRODUCES THE FIRST MAGAZINE RETAIL STORE 
FOR THE ELECTRONIC MAIL-ORDER HOBBYIST! 




************ ** ********** **** ***** * 
t "RED** LED READOVrS: t 
I » low « xoc each t 

Sli* D«Mriptton Sale * 

.127" MAN-3" Sfoi Jl.OO f 

MAN-4* 2 fdi $1.19 1 



* Cat. No. 

■¥ a 7S1B90 
f n TC1503 
I a 7tl273 
X " 7S3093 
Z o 7S3161 
X □ 7S3512 
■k Q 7S2949 
•{i □ 7S!29S0 

id 713483 
o 7S2485 
f □ 7ft22S6 
X 'Common Anodo 



MAN-1- 
MAN-72 oquat- 
MAN-74 equal** 
FND359*- 
FND500* 
FND507* 
727-Dual" 
727-DuaI* 
747- 
"Common Cathodo 



$1.00 
$1.19 
$1.19 
$1X»0 
$1.50 
$1.50 
$2.50 
$2.50 
$1.95 



HEXADECIMAL MICROPROCESSOR n 
LMlircJ::.%:u^Zper^tlA AND CONTROL r\ jttiK 
rip-^UtTCy roiir^H^*^ KEYBOARD KIT' Cs^ 

20keys. 16encoded.4exlernaito «****"«"»"*' •*• * . ^"^ 

be assigned by user. Output 4 bit "'■■ ^ '"^ 

binary. Also, an EXCLUSIVE o 4 bit binary/haxadacimal output plus strobe! 

FEATURE. . . 4 leds dispiav the • Newl Improved design! Saves you time! 

binary output. TTL/CMOS • Keyboard pre-assemMed onto PC board! 
compalible. requires +5. - ««. ^- 

12VDC. Complete kit! Nothing Cat. No. 7»S009 Hexadecimal Kit $34.95 

else to buy! With instructions. Cat. No. 755010 Hexadecimal Wlred$39.9S 



$ > —— »■■■■ ■•■■•••••••••»••■«[ 



********************************** 



DISCRETE LEO'S 


6 for $1.19 


' . Cat. No. 


Description Similar to 


Order m multiples o 752 135 


Jumbo Red MV50S3 


i of « of each type! □ 7S1944 


Jumbo Yellow XC556Y 


D 7S213B 


Jumbo Green XC5S6G 


njUMBO .34" h ^ 752785 


Medium Red XC22 


a MEDIUM .24" ^ JJIlS? 


■Medium Green XC22G | 
Micro Red XC209 


a MICRO .21" Q 78 1948 


Micro Yellow XC209Y 


(T0-18> o 7S2140 


Micro Green XC290G 



■ COMPUTER IT'Vooo 
\ GRADE D 13.000 

■CAPACITORS^ U:S8S 

! Order by C.t. Mo. ' "'JS" 

; 7t5U2.ndv.l„.! = JJOJJ 



WVCD Sale ■ 

50 $2.75 a 

40 2.25 - 

50 2.75 

12 1.50 

75 3.95 

30 2.S0 ■ 

30 3.95 ■ 



li^HIEIIi 

KETBOARD& 
EIVCODER KIT 

Cat. No. 755001 KH $69.95 

Cat. No. 7S5O02 Wred $7S.OO 

Outputs standard 7 bit ASCII; interfaces with most data systems. ■ Uses MOS Encoder ROM! 
Kejboardpre-asscmbled onto PC board, 2 key rollover, Electronic « 7 led Test Feature! 
shift lock and carriage return. 4 modes: Normal, control, shift. » ^ ^^^y Iteyboard' 
ltl'/rV,'^"\'"„';l- Additional. functions can be assigned by user *5 - , Encodes 128 ASCII Characters! 
12VDC, 200 ma. Negative or positive logic, jumper selectable ^ |„..rlarP5 with ALTAIR 

IMSAI, and more! 





LED's display the ASCII code, 

e 10 buy! Size: I.T' x 5 1/2 x 1 1/4". S Iba. 



■■■>• 



Vjwxk Poiver ICs J 



3a itjf n ii_H_iDa.]i ir inr.iDanciaG 

I l^^\ BRIDGE rectifiers: § 

2 AMP 6 AMP 10 AMP 25 AMP Q 

PIV («7S1346) (fr7$24S6) (07S2447) (((752273) H 

□ 50 $ .59 $ J8 $1.05 $1.20 y 
a 100 .65 .99 1.15 1.25 Q 
o 200 .69 1.19 1.29 1.95 t: 

] a 400 .89 1.40 1.79 2.95 Q 

□ 600 .99 1.69 1.95 3.95 U 
i □ 800 1.19 1.95 2.25 4.95 H 
] o 1000 1.25 2^5 230 5.50 ^ 
] Orer by Cat. No. Amperase and VoHase D 

OQPnnnaGEXonnnanDiioLDan 



5PCCTIIA- TWIST * Twisted pairs of brightly 



CABLE 



n Cat. No. 753680 48 cond. 2 ft. $1. 
a Cat. No. 754081 32 cond. 2 ft. $1.98 



O-XXK "ouDnnt jLi k laDLir k j ]DnaDi:iCT[XJOCopD[.]ncoiioc kt 



RIBBOS CABLE 
AT THIN PRICES 

• Ultra-flat! • 28 AWG! 

• Single color! Indexed! 
Order by Cat. No. 7S3939 and conductors 



Cond. Sale 

o 20 8 ft. $1.98 

n 26 6 ft. $1.98 

□ 34 5 ft. 51.98 

n 40 4 ft. $1.98 

u 50 3 ft. $1.98 



Order By Cat. No. 7S3667 & Type No. 

Typo Sale 

74LS00 $.33 

74LS02 .32 

74LS04 .35 

74LS06 .32 

74LS10 .32 

74L511 .32 

_ 74LS13 .64 

D 74LS20 .32 

~ 74LS21 .32 

74LS22 .32 

74LS27 .39 

74LS30 .32 

74LS32 .39 

74LS37 .45 

74LS3S .45 

74L542 1.19 

» L 744.547 .99 

* C 74LS74 .49 

* C 74LS90 .89 
J C 74LS92 .89 
J C: 74LS93 .89 

* n 74LS109 .58 

* a 74LS112 .58 
I G 74LS113 .58 
J a 74LS114 .49 
********** ***** **** * ** ** ****** 



Type 


Sale 


74LS132 


1.19 


: 74L5138 


1.24 


74LS139 




: 74LS151 


1.25 


' 74LS153 




. 74LS15S 


1.2s 


' 74LS1G0 


1.47 


: 74LS161 


1.47 


: 74LS162 


1.47 


■ 741.5183 


1.47 


: 74LS168 


1.68 


74LS169 


1.68 


: 74LS173 


1.68 


' 74LS174 


1.05 


- 74LS190 


1.77 


' 74LS191 


1.75 


: 74L5192 


1.75 


"^ 74LS193 




: 74LS195 




' 74LSig7 




" 74LS257 


1.35 


■ 74LS26e 


.54 


" 74LS366 


.66 


■ 74L5368 


.69 


a 74LS390 






HAlirDT COMPUTER 
IHnLTlTESTER 



1000 ohms per volt 

precision, movement» 



diode protected against 
burnout. Measures DC volts 
0-15-160-1000: AC volts 
0-15-150-1000; DC current 
0-150ma:reaistanceX1000. 
Sensitivity 1000 ohms/volt 
AC-DC. Uses penlite cell, 
not included. Sine 2^/b k 
.IVi X I^'h'*. Wt. 5 ozfi. 
Cat. No. 7S3921 



» 0«00«»» — •■••••••■•••••••••9696»96« 

I POLT PAKS "CHIPS" AWAY J 
I IC ASD CRYSTAL PRICES! I 

I Order by Cat No. 794048 and Type No! t 

ZType Description *-'- * 

• □ICM7205 Stopwatch 
f DAY3-B500-1 6 TV Games 

• □MMSSSO 4'f2 DIgtt DVM 

• □8038C Volt Control Osc. 



sun 
• al 



aKR2376-139 BCD Encoder Rom 
IKR2376-ST ASCII Encoder Rom 
esOMHz Prescaler 
350MHz Prescaler 
Touch Tone Chip 
Char Gen. (sIm 2513) 
Freq Counter pair 
3h Digit DVM/DMM 
60 Hi TImebase IC 
Timebase Xtal 
Touchtone Xtal 
Stopwatch Xtal 



1C90DC 
a95H90DC 
OMC14410 
□ MK2002P 
O7207A/7208 
a|CM7107 
□MMS369 
□3.579MHz 
D LOOM Hz 
□3.2768MHz 



— #66 • — 8»*«690 



■6— » >»6 ■•••••• — 



C-MOS 



Type 

CD4000 

CD4001 

CD4002 

CD4006 

CD4007 

CD4O08 

CD4009 

CD4010 

CD4011 

CD4012 

„ C04013 

Q CD4015 

a CD4016 

~ CD4017 

CD40ia 

CD4019 

CD4020 

CD4021 



Sale 

5.29 

.29 



1.29 



Order By Cat. No. 
752320 & Type No. 
Type Sale 

D CD4022 1.19 

a CD4023 .29 

n CD4024 .79 

n CD402S .34 

L] CD4027 .69 

a CD4028 

a CD4029 

D CD4030 

a CD4033 

n CD4035 

a CD4040 

G CD4041 

n CD4042 

n CD4046 

n CD4049 

G CD4066 

n CD4071 



1.19 
.49 
1.60 



MICROPROCESSORS! 
memories; SUPPORT! 



Order by 



ICG800L 
G 8080A 

□ Z80A 

□ 8008 

□ 1101 
o 1103 

^ 1702 A 
rJ 2102-Ll 

□ 2111 
n 2708 

11 MK4116 
a MK4200P11 
n MM5202 
n MMS203 
n MMS260 

□ MMS262 

□ 8212 

□ 8216 

□ 8224 
a 8228 

□ 8251 
a 8255 



Cat. No. 7S3459 and type 
Description 
8 bit CPU 
8 bit CPU, 2 usee 
8 bit CPU 
CPU 

256 X 1 Stat. RAM 
IK Dyn RAM 
256 K 8 EPROM 
IK X 1 t-o-power RAM 
256 X 4 Stat. RAM 
8K EPROM 
16K Dyn RAM 
4K X 1 Dyn RAM, 3S0nsec 
2K PROM 
2K EPROM 
IK Dyn RAM 
2K X 1 Dyn RAM 
8 bit I/O port 
Bl-dlrect bus driver 
Clock Gen 
System cont. 
Communication Int 
Periph Inter 



Sale 

$19.95 

11.95 

24.95 

9.95 

.69 

1.29 

5.95 

1.69 

5.95 

10.95 

29SS 

3.95 

6.95 

8.95 

.99 

.99 

3.9S 

3.95 

4.95 

9.95 

11.50 

11.95 I 



SILICON POWER 

STVD rectifiers; 

Order by Cat. No. Amperage and vottage. 
50 AMP 
(a7S727) 



12 AMP 
PIV (B7S727) 
D 50 " "" 
a 100 
o 200 
G 400 
o 600 
o SOO 



% .29 
36 
AS 



i .75 
1.10 
1.35 
1.75 
2J5 
2.75 



250 AMP 
(>I7<6SS) 
»4.95 
6.50 
7.50 
•.SO 
10.50 
11.50 



DIP SWITCHES 



Cat. No. 

G 75 3668 

a 75 3669 

G 753021 

D 75 3670 

n 75 3671 

D 75 2677 




♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦ 

□ SN7472 
Q SN7473 

□ 5N7474 
o SN7475 
c, SN7476 

□ SN7483 
;j 5N7485 

□ 5N7486 
o SN7490 
u SN7492 
c SN7493 
n SN74107 

□ SN74121 

□ SN74t23 
a 5N74125 

□ 5N74132 
n 5N74t45 

□ SN74151 
n SN74153 
o SN74154 

: SN74157 
c SN74161 
n SN74164 
a SN74174 

□ 5N74175 

□ SN74181 
^ SN74190 

□ SN74191 
a SN74192 

□ SN74I93 
n SN74195 
c SN74251 

*4444444« 



: TTL'S 

« Type J 

« n SN7400 $C 

«. □ SN7401 

♦ n SN7402 

♦ n 5N7403 

♦ a SN7404 

♦ o SN7405 

♦ a SN7406 
I a SN7407 
I □ SN7408 
« a SN7410 
«. □ SN7411 

♦ n 5N7413 

♦ o 5N7414 

♦ 3 5N7417 

♦ D SN7420 

♦ □ SN7427 

♦ n SN7430 
I :: 5N7432 
i :: 5N7437 
i n SN7440 
« Li SN7441 
« n SN7442 

♦ G SN7445 

♦ u SN7446 

♦ □ SN7447 
« □ SN7448 

♦ Q 5N7450 

♦ n SN7451 

♦ a SN7470 
♦♦♦♦♦♦♦♦♦♦♦♦*« 



♦♦♦♦♦♦ 
.26 



.49 ♦ 

.39 ♦ 

.83 ♦ 

.89 ♦ 

.63 ♦ 

.63 ♦ 



.93 

.88 
1.95 ♦ 
1.15 ♦ 

.99 ♦ 

.83 ♦ 

.83 

.75 

139 

♦«4444 



EECO 10-POSITION BCD 
THUMBWHEEL SWITCH 

l-a-4-M Ut'D encoding: 
Positions labeled 0-7. F, L. 3 »Or 

IF coded for S. L coded for $4. 
9 1, While numeriil.f on a 
black background. Eeco 800 (_] 
.series. IVa x 1 V4 x V3".<t* Jtt% 
Cat. No. 753846 91.47 



********* LI^£/^P3 ********* 



Type 

□ Cms 



M301H. V 
o LM307H, V, N 
□ LM308H, V 
cj LM309K 
o LM311H, V 



GIANT SALE! MICRO-MINI Cat. No. Contacts Sate 

TOGGLE SWITCHESo 7|3,36 |Pst 5J^| 

» 3A, 125VAC contacts or bettern 755085 SPDT* 139 
a Complete with mounting n 754037 DPDT 1.45 

hardware! "Center oH 



.***i*j;it:?«**: 



♦♦♦•♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦ 

: IC SOCKETS : 

^ as low as 17^ «>• t 

• e Low profile, solder tail. ♦ 

♦ ti 752123 8pl«minidip$ .17 ♦ 

♦ n 751308 14 pin dip .19 * 

* D 751309 16 pin dip JZ2 T 
□ 783378 18 pin dip 



_._..^************ —.;•»««»»* * ° /»id7» iBptnoip ^9 ^ 

.******J{Sr'cTHOL* SKINNYTHIMS" J ; »♦♦ ♦♦♦♦♦«: 

«Ohiin **^*' ,„.«,lri>.T shi.fl _ ,_, Bt! I 

jD lO'/. ■'»"Tn\;ii i>""' "'2 '""^ * ♦ MOTHHRBOA 

te iK::s fSi-^fc -■';U«i*i5'^*:pi.~X«p."t edge_conne^ 




«n 2»"D lOK' 



M« TS 3863 25 turn upril***- J-r^ _- « 



m 



IMC 'VPEWEE" 
,, BOXER FAN 



Quiet! 

Oelivera 

Audible 



n:s^'-s 



D 
S2.50 



RD 
CONNECTOR 

106 pins (53 each aide). 
Use with IMSAI & ALTAIR! 
0.J26" pin clrs, goldplated 
%" wire wrap leads. Open 
ends, fit wide PC boards. 
8 oza.Cal. No. 783987 



"MICRO-TONE" 0^88 
AUTOPATCH ^^ 

ENCODER KIT "" 

Only 2 l.'» s ! .V8 x i,'2", small 

enough t^) mount in a mike! Snap • Complete 

action bubble keys contact jn Its own 

Features output level control. _,_. _^., .. 

xtal controlled d i K i I a 1 1 y •^"•-*'''W''«*' 

synthesized tones, on-chip , Family! 

oscillator. Requires 4.5 to 5.5 ^ Frlanos! 

VDC. Complete kit! Nothing else 

to buyl Wt. 12 oz, • 

Cat. No. 754086 hit $26.88 EmerEency! 

Cat. No. 754087 wlred$32.9S 



I □ LM340T-12V 

X D LM340T-15V 

« □ LM340K-5V 

i a LM340K-12V 

« a LM340K-15V 

« o LM322N 

* a LM324N 

* a LM339N 

* □ LM377N 
Z a LM379N 



1.19 
1.19 
1.19 
1.19 
1.19 
1.19 
1.19 
1.19 



1.19 t 

1.191 
.445 
.69* 
.65 V 

1.40 « 
.39* 
.22* 
-29* 
.42* 
.29 + 
.59* 
.69 X 

1A9Z 
.351 

1.19( 
.69* 
.75* 

1.50« 

■-i^^±±*:t****** ** 



□ LM3S0N 
a LM381N 

□ LM5S5V 
rj LMS5SV 
a LM565N 
o LMS67V 
L: LM703H 

a LM709H. N 
n LM710N 
n LM723N 
n LM741H,V. N 
D LM747H, N 
r: LM 1458V 
'- LM1800N 
I LM3900N 
1: LM39009V 

LM7S491 
■; LM75492 
;J PA263 



10 AMP POWER TAB SCR'S, piv sale 
TRIACS. QUADRACSrcatHo o !So ^H 

SCfl'S 751730 n 200 .88 

Order by Cat. No. TRIACS 751448 d 400 1.19 

and Voltage QUADRACS 7StS90 g 600 1.59 



■■■■■■■■■■■■■■ 

TRANSFORMER 
SALE ^^^^ 



a^of^i 



■■■■«■■■ 



I ;&*"■">« pots- *>*.5o 

• Chrome handle and hnoH, **: «> "^ 

-r?!L!!!!i'*3«08A 



Cat. No. 
n 78 3399 
D 75 3814 
U 7$ 3412 
n 75 4029 
ri 7S3875 



iXOVAC Primaries 

Output V. Al 



500m 
lA 
3 00m 



Metal encased 
Open frame 
Open frame 
Open frame 
Isolation 



Sate 

Each 

51.98 

52.49 

51.95 

$2.49 

S1.19 



■■■■■■■■I 



Noi«e ^Level! Sleeve | 
bearings rated, for lClyea|8^b^e. 



XN^WiO Epo%^ Rectifiers 



For hTfI andComputersJiSVAC^ 



Cat. No. 
n 75 2377 

□ 7S2378 

□ 7S2379 

□ 752380 
n 75 2381 

□ 752382 
D 752383 



1N4001 
1N4002 
1N4003 
1N4O04 
1N4005 
1N4006 
IN4007 



PIV 
50 
100 
200 
400 
600 
SOO 
1000 



Price 
10 lor $.65 
10 for .75 
10 lor .85 
10 for .99 
10 for 1.29 
10 for 1.39 

10 for 1.49 



CATALOG 



WRITE POLY PAKS 1978 

FOR 

FEATURING: 

• Computer Components! 

• Over 400 Assortments! 

• Digital Clocks. DPM's, 
and Stopwatches! 

a H(-FI Stereos-Speakers! 

• Solar Energy! Semi's! 

• Test Equipment! 
» Fiber Optics! Plus More n' More! 



) COPYRIGHT 1978 - POLY PAKS INC 




Terms: Add postatre Rated: net 30 
Phone : Wakpfifld. Mass. (617) 245-3829 
Retail: 16-18 I'el Carmine St.. Wakefield. 
MINIMUM ORDER — $6.00 

POLY PAKS 

P.O. BOX 942 -S7 



C.O.D'i 



rtn P.O. BOX9az-s>7 
c:^ LYNNFIELD, MA. 



Circle 303 on inquiry card. 



BYTE July 1978 203 



Circle 353 on inquiry card. 




$199.95 

AS IS 




IBM® Selectric-Based 

I/O Writers 

Excellent Hobby Printers 



$249.95 

WORKING & 
CLEANED 



Series 72/731 
Heavy Duty 
8y2" Flatten 



All Solenoids 
Original Documentation 
While Supply Lasts 



SUPER SALE 

These terminals are from a large airline reservation 
system. They are heavy duty and were under continuous 
maintenance. The units have been in storage. We make 
every effort to ensure that all essential parts are included. 
Most work when plugged in. No warranties are given or 
implied. 
Conversion Kits. 

1 . Conversion instructons, P C board for printer only using soft- 
ware approach $59.95 

2. I/O kit makes the unit into a conversational terminal. Instruc- 
tions, P C board, components for a parallel or RS232 interface. 
Will work with any IBM terminal $249.95 

3. Completely converted unit and assembled interface for I/O us- 
ing kit $999.95 



Card reader by HP with RS232 interface $299.95 

Printec line printers, parallel interface $1 500.00 

Honeywell 516 & 316 mini's, make offer, Cables, used 11 
conductor, 1 00 ft with connectors $9.99 

Electronic parts and circuit boards 1/4 lb bag $4,99 



Check, Money Order, Cash. Personal checks require 3 
weeks to clear. No COD's. Units shipped UPS or PP 
collect. Prices Net FOB Tulsa 

SUPER SURPLUS SALES 

P.O. BOX 45944 TULSA, OK 74145 1-918-622-1058 




4101 STATIC, ni IMHH «l9i>1 N-MOJ UM 

OENERAL 
DESCRIPTION 

P«i1 NumtMr 4«01 

ita4KBemicon- 

ductor random ^ 

Bccoas memorY ll 

organizad as 4096 Vbit words. It it fully static and 

' a«ds no clock or rafrash pulsas II raquiraa a 

ringia * 5 volt powar supply and is fully TTL com- 

patibla on input and output tinas. Tha 4601 ia 

packaged in a convanient ISpindual-in-lina 

package. 

FEATURES 

■ Singla ^ 5V Powaf Supply 

■ 4KX1 Organization 

■ Raolacaa 4 t024xl Sialic RAh4a 

a Complalaly Static-No Clocks or Rafraah 

a 18 Pin Package 

a Access/Cycle Times 600 naac mak 

■ 250 mw Typical Operating Power 

■ Separata Data In and Data Out 
a TTL Compatible I/O 

a Tftree Slate Outputs 

a Data Bus Compatible I/O Function 




4S04 STATIC, HI IN/OUT 1024i4 N-HOS RAM 

GENERAL 
DESCRIPTION 

Part Number 4804 
It a 4K semicon- 
ductor random 
access memory 
organiiedas 1024 4-bii words. It is fully sialic and 
needs no clock or refresh pulses It requires a 
Single ' 5 voll power supply and is fully TTL com- 
patible on input and output lines. The 4804 is 
packaged in a convenient 18 pin dual-m-lme 
package 

FEATURES 

■ Single • 5V Power Supply 

■ 1Kx4 Organization 

■ Replaces 4 1024x1 Sialic RAMs 

« Completely Static-No Clocks or Relresh 

■ ISPin Package 

■ Access/Cycle Times 600 nsec max 

• 250 mw Typical Operalir>g Power 

• Common I/O Bus 

■ TTL Compatible I/O 

■ Three Slate Outputs 



\Tr/ tPi-tek, inc. 

\ >/ 7806 Nwih 27th A«tnue 

V Phomix, AriionaSSOSI 



INTEGRATED TONE RECEIVER 



7806 Noritt 27tli Atranue 
Pboania, Aritona 85031 
16021 8060362 

SigiMHo 2S04TA 1024 bit S.R. nwnary (I404A)... .SO 

MCM6571PCharacUf GifMrilar 9.^5 

MCM6571APCh>ncUfG«Mnlor 9.95 

MCI44aai>Tiliphon« Rotary Pulnr tO.S8 

MC14419PToud< Pad Convener for 14400 4.2S 

MC1441 IP Baud Rata Ganaralor 11.88 

MC14412VP CMOS Madam Chip ie.86 

MU57109NNumb<r Cruncher Micro 18AS 

74C915 7 Segment to BCD Convartar 2.80 

74C922 16 Key Kaybaard Encoder 8.35 

740923 20 key Keyboard Encoder 8.46 

74C925 4 Decade Counter w/latchei 12.00 

74C926 4 Decade Counter tw/carry 12.00 

740935-1 3'A Digit DVM CMOS ChiD 18.98 

IN4003 200V lamp 12/81.00 

IN4a04 400 V 1 amp 10/81.00 
IN414a Hi Speed Sijnal 15/81.00 1OT/$5.00 

D.600 115 V, 100 mA Hi Spaed Signal 20/81.00 

D2131 200 V. 2SA Stud SBc 

02135 400 V, 2SA Stud 1.00 

02138 600 V. 25A Stud 1.S5 

D3289R 200 V. 160A Stud Anode S.8S 

03909^4 SO V, 46A Fast Recovery 2.00 

IN4732A'47A 1W 5% Zaners 4/81.00 

13 Assorted Brand New Zener Diodes 1.00 

50V 3 amp Epoxy Bridge 79t 

200V 30 amp Bridge 2.00 

600V 4 amp Epoxy Bridge 1.49 

600V 3 amo Stud Bridoe .89 

SI-2 2aOV. I.SA Gold Leods 1S/$1.00 

01A0030 30V DIAC 10/81.00 
VOLTAGE REGULATORS 

7a05^060ai2 1S-24TO720 95< 5/84.60 

78L05A 12 15 4* 100mA TO-92 Plosflc 

78H05KC 5V 5A TO 3 

78H12KC 12V 5AT03 

78H16KC 15V 5AT03 

Lm317K 1.5AArf;usra6/eT0 3 

Lm317T 1 SA /<d/u«a6te TO 220 

Lm317MP .SAAdiustab/etO-iOi 

TL430C Adjustable Zener 7'ft/n* About It 

TL497C Siivitching Reg. fit Inductor 

RCA CA 3085 100 mA Adjustable 



S8.95 



4«I1 or 4804 4K RAM's 

8/S60.00 16/1100.00 



MK5102(N)-5 



a Detects all 16 stwKtord OTMF digits 

O Rsquires minimum axtemal parts count for 

minimum syitw* coat 
D Uses inexpensive 3.579545 MHi crystal for 

rettrvnce 
a Digital counttr detection with period averaging 

insures minimum false response 
O 16-pin package for hi^ systefn density 
O Single supply 5 Volts t 10% 
a Output in either 4-bii binary cod* or dual 2-bit 

row/column code 
D Latched outputs 

DESCRIPTION 

The MK5102 is a monolithic integrated circuit 
fabricated using the complententary- symmetry MOS 
(CMOS) process. Using an inexpensive 3.579545 MHz 
television colortwrst crystal for refervrKe. the 
MK5102 detects and decodes the 8 ttandard DTMF 
frequerKies used in telephone dialing. The require- 
ment of only a single supply and its construction in a 
16-pin package make the MKS102 ideal for appli- 
cationa requiring minimum size and external parts 
count. 



DETECTION FREQUENCY 



OtMri Ml iMn IIO <>ll loiai 
ntntfllns. 

Any iMunai wtH M W cMck, n*t en 



50< 

9.15 

9.15 

9.15 

, 4.98 

3.80 

13.95 

1.50 

9.50 

.60 

•■mpoiclly ou< o> ilock on an Ham, 
■n kKk MMr. it ■>• cannot inip In ] 
■ notitiM O' 1M aKMCtM >M«plna «ai 
Fiin I poftae* MM carfl aiiih ■mien l 

I (fitpplnf onty In USA, CanaOa ar 
iw»k>9 <(irii cUH, ipacUi naiv«>in«, aic 
• ■capt CanaM an« Manlco) oMlmaM a' 



Low Group to 


High Group i« 


Row 1 - 697 Ht 
Row 2 - 770 H> 
Row 3 - 8S2 Hi 
Row 4 -941 Hi 


Column 1 - 1209 Hi 
Column 3 - 1477 Hi 



JULY SPECIAL -TIL 31 JULY 

MK5I02N-5 $33.00 

Spec 40 

600 :600 C.T. phone transrormer...$1 .50 
P. C. BOARD TKMINAL STUIP 
Motd*d body oncloaAs postivo screw ocfrivotod clomp 
which will accomodate wire sizes 14-30 AWG. Gvitacts 
ar>d pins ore solder plated copper. Pins are on .200 
in<^ (S.OSmM) for stortdord P. C. mounting. IQAmp 
rotirig. Compare our prices before you buy. 



4pola 


TS-2S04 


.99 


8poU 


TS-2508 


1.49 


12 polo 


TS-2512 


2.19 



0^ 



204 July 1978 © BYTE PuMiutions Inc 



Circle 381 on inquiry card. 




S.D. COMPUTER PRODUCTS 



AN EMPIRE IND CO 



P.O. BOX 28810B 



DALLAS, TEXAS 75228 



EXPANDABLE EPROM BOARD 

16K OR 32K EPROM $49 95 W/OUT EPROM 
Allows You to Use Either 2708s For 16K ot Eprom or 
2716's For 32K of Eprom. 

KIT FEATURES: 

1 All Address Lines & Data Buffered 

2. Quality Plated through P-C. Board Including 
Solder Mask and Silk Screen 

3. Selectable Unit States 

4. On Board Regulation Provided 

5. All Sockets Provtded W/Board 

WE CAN SUPPLY 450As 2708's AT $11.95 
WHtN PURCHASED WITH BOARD. 



EXPANDORAM 

THE ULTIMATE RAM BOARD 

32K FOR $475.00 



-HSl.OO 

. 259.00 

367,00 

475.00 



THE 32K VERSION USES THE MOS 




4K LOW POWER RAM KIT 
The Whole Works - $79.95 

Fult Buffered - on board regulated ■ reduced 
power consumption utilizing low power 21L02-1 
500ns RAMS - Sockets provided for all IC's. 
Quality plated througfi PC board. 




I^«*!,.;f.^VA^ .'Ifn" J'^n°..r*^.'^L ^i BOARD TO A MAXIMUM OF 65K 



BOUNDARIES AND PROTECTION 
UTILIZES DIP SWITCHES P t, 
BOARD COMES WITH SOCKETS FOR 
32K OPERATION 



SZ81 00 
519.00 
757.00 

995,00 



THE 64K VERSION USES THE MOS- 

TEK MKdlie RAM AND HAS ISK 

K tirFPI OF FITHFR BK BOUNDARIES AND PROTECTION & 

nrifiK'.; vnilR nPT%N RV MFRF UTILIZES DIP SWITCHES P. C. 

?? purchasing" more' RAM JmPS IPrOPE'RMJoN'"'" '°''"' "" 



FROM SD COMPUTER PRODUCTS. 



LOOK AT THE FEATURES WE HAVE BUILT INTO THE EXPANDORAM! 



• NO WAIT STATES REQUIRED 

• NO CYCLE STEALING NEEDED 

• ON BOARD REGULATION 

• CONTROL, DATA S. ADDRESS INPUTS 
UTILIZE LOW POWER SCHOTTKY 
DEVICES 

• DESIGNED TO WORK WITH Z-80, 
8080, 8085. CPU's 

ADD $50.00 TO ABOVE PRICES FOR FULLY ASSEMBLED AND TESTED BOARDS 



• MEMORY ACCESS TIME IS 375 ns 

• MEMORY CYCLE TIME IS 500 n 

• POWER REQUIREMENTS ARE: 

8 VDC 400 MA DC 

18 VDC 400 MA DC 

—18 VDC 30 MA DC 

• ON BOARD INVISIBLE REFRESH 



Low Cost 

Cassette 

Interface Kit 

$19.95 



Features Play and record K.C. Standard 2400/1200 Hi 
tapes, 900 Baud. TTl I/O Compatible, Phase Lock Loop, 
Both 22 Pin ConneetDt and 8 Pin Moie» Connector. 
Comes parliilly afisembled OsciMalor and phase lock 
loop pre luned to K C. Standard. Selector switch sends 
cassette data ot autiliary input data to mi 
LEO indicates logic 1 level. 




8K LOW POWER RAM 
$159.95 



JLLY ASSEMBLED AND TESTED NOT A KIT 
isai — AHaif — S-100 Buss compalible, uses io* oowet 
alic 21L02-500ns tutly butlefeU on board regulated, 
lalily plated Itirough PC Board including solder mask 
IS dip s*itcfies tor address seiecl 



■Add $30.00 for Q 

250ns RAM operation 




Z-80 CPU BOARD KIT 
Complete Kit $139. 



:^^jii' '*■ 



CHECK THE ADVANCED FEATURES OF OUR Z-80 
CPU BOARD: Expanded set of 158 instructions, 
8080A software capability, 
operation from a single 
5VDC power supply; always 
stops on an Ml state, true 
sync generated on card (a 
real plus feature!), dynamic 
refresfi and NMI available, 
either 2MHZ or 4MHZ op- 
eration, quality double sided plated through PC 
board; parts plus sockets provided for all IC's. 
•Add $10. extra for Z-80A chip which allows 
4MHZ operation. 




NEW FROM S.D. 
"VERSAFLOPPY"' KIT 

THE VERSATILE FLOPPY DISK CONTROLLER 
ONLY $149.00 



FEATURES: IBM 3740 Soft Sectored Compatible- S-100 BUS 
Compatible for Z 80 or 8080. Controls up to 4 Drives (smgle 
or double sided). Directly controls the following drives: 
1- Shugarl SA400/4SO Mmi Floppy 

2. Shugart SA800/850 Standard Floppy. 

3. PERSCI 70 and 277. 

4. MFE 700/750. 

5. CDC 9404/9406. 

34 Pm Connector for Mini Floppy. 50 Pin Connector for Stand- 
ard Floppy. Operates with modified CP/M operating system 
and C Basic Compiler. The new "Versaf loppy ■ from S.D. 
Computer Products provides complete control (or many of 
the available Floppy Disk Drives, Both Mini and Full S\i«. 
FDI771B-1 Single Density Controller Chip, Listings for Con- 
trol Software are included in price, 

FD 1771B1 CHIP ALONE $39.95 



Z80 STARTER KIT 
LEARN COMPUTERS FROM THE START! 
SIMPLE, STEP BY STEP LEARNING. CONSTRUCTION, 
PR0GRAMMi;4G, OPERATION, MEMORIES, INTER- 
FACING, COMPUTING, AND CONTROLLING WITH 
AUDIO CASSETTE INTERFACE CAPABILITIES. 
Complete Kit includes: Key board and Display; Z80 
Central Processing Unit; Instructions; Operation Man- 
ual; Learning Guides- 
Features: Powerful Z80 CPU with 158 instructions • 1024 
Bytes (Expandable to 2048 Bytes ON BOARD) of RAM • 
2 BiDirectional Input/Output Ports with Handshaking 

• Kansas City Standard Audio Cassette Interface for 
Program Storage • Hexadecimal Keyboard and Display 

• Wirewrap area for custom circuitry • S-100 Connector 
on board tor Memory and I/O Expansion • 2716/2758 
PROM Programmer • -'Z-BUG" Monitor ROM (Including: 
Memory, Port and Register Examine and Change Com- 
mands; Breakpoints; Single Step Capability; Audio Tape 
Load and Dump; Execute user program Commands.) 
Many more unique features. The best computer edu- 
cational kit on the market , . . the complete computer 
and educational package for only (199.00. (Available 
June 1978)- 



INTRODUCING THE SBC-100 

(The Z-80 Based. S-100 Single Board Computer) 

$349.00 



FEATURES: 

• No Front Panel Needed 

• 2-80 CPU (2 or 4 MHZ) 

• IK RAM 

• 4 ROM/PROM Sockets tor 4K/8K of Memory 

• SYNCHRONOUS/ASYNCHRONOUS Serial I/O w.Ih 
RS 232 and Curreni Loop Inlerface and Software 



• Programmable Baud Rate 

• Parallel Input Port 

• Parallel Output Port 

• 4 Channel Timer/Counter 

• 4 Vectored Interrupts 



RAMS 



8/15 95 

14 95 

8'S4 CX) 



MK 4115 -8K 

74S 200 ■ 256 



CPU'S 



Z— 80 includes manual 
Z— 80A includes manual 
8080ACPU6BIT 
8008 CPU 8 BIT 



PROMS 



1702A ■ IK • l,5ui 3.95 or 10/35. 

2708 ■ 8K • 450ns 14.95 

5204 ^K 7.95 

82S129 — IK 2.50 

2708U 8K signatics 650ns . . . .9.95 



O. E. M. SPECIAL 



ASK ABOUT SPECIAL OEM DISCOUNTS ON THE SD COMPATIBLE SET 



SDC 100 — SINGLE BOARD COMPUTER 

VERSAFLOPPY' " FLOPPY DISK CONTROLLER 

EXPANDORAM — 32K RAM 

EACH KIT IF PURCHASED SEPARATELY TOTAL S973.00 
ORDER ALL 3 KITS TOGETHER FOR 

$899.00 

Thi» Powerful Threesome Operates Together to Form A Comolete Computer 



$349 OO 
$149 OO 
$475 OO 



for Your System. 



Z-80 

Programming Manual 



IN DEPTH DETAIL OF 

THE Z-80 CPU 

MICRO-COMPUTER 



S. D. SALES SPECIAL 
$9.95 



S.D. NOW HAS SOFTWARE FOR IT'S CUSTOMERS 



CP/M DISK OPERATING SYSTEM . 

CP M IS a powerful disk operating system which has become an industry standard 
disk based FORTRAN and BASICS This package includes a CP/M diskette (mmi oi 
SBC 100/ VERSAFLOPPY EXPANtXJRAM board set. Complete documentaljon is n 
islered trademark of Digital Research Corp . Pacific Grove. CA. 



$99.95 



t IS compatible with severa 
full size) adapted for S D ■ 
eluded ( I CP/M IS a reg 



Z-80' DISK BASED ASSEMBLER $69.95 

Runs on ANY CP/M based disk system Assembles 
the official Ziiog-Mostek Mnemonics, Contains ex 
tensive set of pseudo ops. Available on mini or 
full size diskette. 



VERSAFLOPPY' ' CONTROL FIRMWARE . . . $24.95 

Provides control for VERSAFLOPPY and boots up 
CP/M. This runs on Z 80. 8080 or 8085 based 
computers. Available m 2708 or 2758 prom. 



SD MONITOR $49.95 

Powerful monitor tor SBC 100 smgle board ■com 
puters Includes all VERSAFLOPPY control firm 
ware Comes in 2716 prom. Available in 4-6 weeks 

VERSAFLOPPY DIAGNOSTIC PROGRAM . . $24.95 

Provides routines which are hetpful m checking out 
a disk based system Available m 2708 or 2758 



COUNTER CHIPS 



MK50397 6 Digit tiapsed timer 8 95 

MKS02S0 Alirm clocli 4.99 

MK50380 Alarm chip 2.95 

MK5039S 6 digit up/dn. count. 12.95 

MK5002 4 digit counter 8.95 

MK5021-Cal. chipsq. root 2.50 



* 



SUPER FLOPPY SPECIAL 

S. D SALES- VERSAFLOPPY S 100 CONTROLLER BOARD PLUS 
SHUGART SA 400 FLOPPY DISK DRIVE INCLUDING CABLE FOR ONLY 

$479.00 



* 



MICROPROCESSOR 
CHIPS 



8212 ■ 1/0 port 

8214 — P.I. C 

8216 — Non Invert Bus . . . 

8224 — Clock Gen 

8226 — Invert Bus 

PIO for Z— 80 . 

CTC (or Z— 80 

8228 Sys. Controller 

8251 Prog. comm. interfact. 

8255 prog. prep, intertace. . 

8820 Dual Line Recr 

8830 Dual Line Dr 

2513 Char. Gen 

8838 Quad Bus. Recvr, . . . 
74LS138N— 1/8 decoder 
8T97.Hei Tri-State Buffer 

1488/1489 RS232 

TR 1602B Uart 

TR 1863 Uart 

FD 17718-1 



.3.50 
12.95 
495 
4.95 
3.95 
14.95 
14.95 
8.20 
10.95 
13.50 
1.75 
1.75 
7.50 
2.00 



1.25 
1.50 
3.95 
8.50 
39 95 



CMOS 



4001 
4002 
4011 
4013 
4016 
4017 
4020 
4022 
4024 
4027 



19 
19 
19 
32 
32 
95 
97 
97 
75 
39 



4029 
4042 
4047 
4049 
4069 
4071 
4076 
14518 
14528 
14529 



!I9 
69 

1.50 
35 
23 
19 
97 

1.10 
85 
85 



CALL IN YOUR BANKAMERICARD 
(VISA) OR MASTER CHARGE OR- 
DER IN ON OUR CONTINENTAL 
TOLL FREE WATTS LlNEr 

1-800-527-3460 



Texas Residenu Call Collecl: 

214/271-0022 

DEALER INQUIRIES INVITEDI 



(All prices subject to ctiange 
wittiout Dnor notice.) 



NO CODs. TEXAS RESIDENTS ADD 
5% .SALES TAX ADD 5% OF ORDER 
FOR POSTAGE & HANDLING OR 
DERS UNDER $10. ADD 75c HAND 
LINGFOREIGN ORDERS - U. S 
FUNDS ONLY! 



Circle 31 5 on inquiry card. 



BYTE July 1978 



205 



Unclssaifiei^Ac^B 



TRADE: BYTE, volume 1, number 2, good condi- 
tion, for Dr Dobb's Journal of Computer Calisthen- 
ics and Orthodontia, volume 1, number 1, I need 
the article on NIBL BAS/C for the SC/MP chip. 
Joe Price, POB 543, Olton TX 79064. 

FOR SALE; TRS-80 LEVEL-I BASIC tapes and 
lists: Star Trek (needs 12 K memory), list $7, 
tape $9.95: Biorhythm (4 K), list $4.50, tape $7; 
Lunar Lander (4 K), list $3. tape $5. R Menzies, 
7106 Colgate Dr, Alexandria VA 22307. 

FOR SALE: ASR 32 Teletype with stand, paper 
tape punch and reader, documentation; excellent 
condiiion, $325. David Shorthill, RFD #2, Wells 
ME 04090. (207) 646-5465. 

TERMINAL: Texas Instruments 725, 30 cps, 
hard copy, built in modem and coupler, rugged 
portable case. Very quiet, popular professional 
terminal, $775 plus shipping. Also memory: 
Solid State Music, 8 K, static, 500 ns (no waits), 
assembled, works, $150, Wright, POB 7576, 
Menio Park CA 94025 (415) 854-5678. 

FOR SALE: Heathkii computer system. System 
includes; H8 computer, H9 video terminal, 8 K 
memory, all standard Heathkit software plus 
extended BASIC. Completely assembled and 
tested. Asking $1400. Call or write Paul Randazzo, 
37 Maxwell Dr, Wethersfield CT 06109 (203) 
529-0530. 

WANTED; Back issues of CACM, JACM, and 
JCCs. W Hutchison, Princeton Arms N 191, 
Cranbury NJ 08512. 

FOR SALE: Shugart SA400 minifloppy disk drive 
and ten minifloppy disks, $390, (no controller 
or power supply). Working video interface per 
February 1976 BYTE, $100. DECwriter keyboard, 
$50. Power supply, $35. Case, $42. Parts for 
6800 processor board including 6800, 2x6810, 
2x6820, 2708, wire wrap sockets and support 
ICs $150. Everything except disk, $310. James 
Thomas, POB 26, Sandv Spring MD 20860, 
(301) 774-7686. 

FOR SALE: DEC PDP8e modules and peripherals 
DK8EP, $375. AD8 16 channel A/D $875. DEC- 
writer $1050. Omnibus expanders, power supplies, 
KL8Es; lots more. Send for list and tell me if you 
have anything for trade or sale. I will repair any 
DEC part or build custom interfaces or modules. 
J Simpson, POB 632, W Caldwell NJ 07006. 

FOR SALE: Thinker Toys "Speakeasy" board 
assembled, RS-232 serial port used, $100. Paul 
Lamb, 13101 Parson Ln, Fairfax VA 22030. 

FOR SALE: The Northstar Users group has over 
230 outstanding programs including real estate, 
investment, business, debugging aids and games, 
t will copy these public domain disks for $5 per 
disk plus the cost of a disk (or send a disk). About 
15 programs on each disk. For a list of programs 
and details send SASE to J Dvorak, 704 Solano 
Av. Albany CA 94706, (415) 527-7730. 



Readers who have eQuipment, software or other 
items to buy, seft or swap should send in a dearly 
typed notice to that effect. To be considered for 
publication, an advertisement should be clearly 
noncommercial, typed double spaced on plain 
white paper, and include complete name and 
address information. These notices are free of 
charge and will be printed one time only on a space 
available basis. Insertions should be limited to 100 
words or less. Notices can be accepted from 
individuals or bona fide computer users clubs only. 
We can engage in no correspondence on these and 
your confirmation of placement is appearance in 
an issue of BYTE. 

Please note that it may take three or four 
months for an ad to appear in the magazine. ■ 



FOR SALE Floppy Tape Peripheral complete 
with 10 board, 8 tapes, new and used. Uses stereo 
8 track cartridge. Each cartridge can hold one 
program per track or 8 per cartridge. Program 
length limited only by tape length. The used tapes 
have 5 or 6 programs on each and are included 
free. They are ready to run and cover Star Trek, 
Othello, other games and technical programs. Will 
interface to most microcomputers, schematic 
included. Will ship UPS. $100, R Mendelson, 27 
Somerset PI, Murray Hill NJ 07974. (201) 464 
5244. 

FOR SALE: Teletype model 33ASR, Excellent 
condition, $600. ALTAIR 8080a, with 8 K mem- 
ory, TTY and cassette 10 boards. Factory perfect 
condition, all MITS, $580. Selectric based type- 
writer with paper tape RDR/PCH. Nice TTY 
alternative, $480. All for $1500 Andrew Frankford, 
2014 Marietta Av, Lancaster PA 17603, (717) 
299-2456. 

TELETYPE FOR SALE; (All 8 level ASCII) Model 
33ASR (new), $1000, Model 35KSR (new), $1500. 
Model 35ASR (used, very good), $1500. Model 35 
reperf and reader set, $425. Parts for Model 33 and 
35 machines, gears, modems. Model 28 Baudot 
machines. Send SASE for complete list and prices. 
Lawrence R Pfleger, 2141 N 52nd St, Milwaukee 
Wl 53208. 

PROGRAM EXCHANGE: Programs are now avail- 
able, in source form, to run on most any home 
microcomputer. These programs corrte from various 
sources and are written in BASIC and other 
languages. In addition, our club needs other pro- 
grams that you may have developed, making them 
available to other hobbyists for fun, enjoyment, 
and practical use. If you can make available such 
programs we want to hear from you. Please write 
to us soon. For complete descriptive literature and 
a list of currently available programs, send $1 to 
cover copy and mailing costs to: Mikel Home 
Computing, POB 17105. Irvine CA 92713. 

FOR SALE: "Elf" microcomputer trainer, $60 
complete. Built from Popular Electronics articles. 
Carefully wire-wrapped on Vector board; all ICs 
socketed. Full hexadecimal keyboard in out- 
board module. Hexadecimal display shows 10 
byte and memory address. All modifications fully 
documented. RCA User's Manual, article reprints, 
much extra data included. Bob Levine, 32 King 
St. New York NY 10014. 

FOR SALE: MMD-1 by E&L Instruments, $250, 
Bug Book V included (6 units). Contact (805) 
522-5276, after 6 PM. 

FOR SALE: BYTE September 75 through 
December 76 excluding January 76. All in per- 
fect condition. Make an offer. Fred Henry, 104 
Heathercreek Dr, Plainfield IL 60544, (815) 
436-6111. 

FOR SALE: North Star BASIC programs: Corres- 
pondence Editor: $5, Stock Market Analysis 
package: $5, Mailing list and random access pack- 
age: $3, Spacewar game package: $3, plus; Stock 
Market data on 30 heavily traded companies on 
North Star disk. Includes: P/E, price, volume, and 
percent yield, weekly averages for 1977: only 
$25 for all 30. Send blank disk, or include $5.25 
for disk. Write for complete list. Herbert Schildt, 
1007 N Division, Urbana IL61801. 

TRADE: 12 slot ALTAIR 8800A with HD power 
supply plus 10 slot IMSAI for factory assembled 
Altair 8800B. Both units fully socketed and fac- 
tory checkout. Ken Roberts, 10560 Main, fel5, 
Fairfax VA 22030. (703) 591-6008 or (703) 
378-7266. 

FOR SALE: PORTACOM briefcase ASCII printing 
terminal w/modem, keyboard, instructions, $595. 
DEC PDP8es, modules, ASR33s, ham gear, free 
lists, buy, trade, repair, design also. K2DCY, 
1 1 Squire Hill, N Caldwell NJ 07006. 

FOR SALE: Digital Group Z-80 four board system 
including CPU, 10, TV cassette and mother board 
assembled. Two 8 K memory boards, one with ICs, 
both with sockets, unassembled. Complete 
assembly plans and documentation. Going to 
college, must sell. $750. Richard Yero, 12323 
Algonquin Rd, Palo Park IL 60464 or call (312) 
448-2609 after 4:00 PM or weekends. 



FOR SALE. Altair 8800a with IMSAI 20A power 
supply installed in original cabinet. With serial 10 
board, Tarbell 1 702A prom board, and 4 to 32 K 
programmable memory. Everything works 100% 
and software is included. Tell me what you want 
and I will quote a price, or make me an offer. For 
more information call (518) 456-8717 or send 
SASE to Michael Favitta, 4 Sherwood Forest Rd, 
Albany NY 12203. 

FOR SALE. NCR high speed paper tape punches, 
110 V, 60 Hz, used but overhauled about 100 cps 
(according to technical manual), self-contained 
cabinet, tape spooling mechanism built-tn, eight 
tracks, weight 40 lbs. Delivery within 5 weeks after 
your order comes in (ie: 5 weeks till you have it). 
Price $200 including freight, collective orders from 
clubs (minimum 5 punches) $150 per punch plus 
$100 for freight. Order accompanied by crossed 
checks should be sent to TIME OUT, Siegfried 
Manfred Rambaum, Rossdoerfer 44, 6100 
Darmstadt, GERMANY. 

FOR SALE: Control Data 200 UT remote batch/ 
interactive terminal, equipped with a 14 inch CRT, 
63 character keyboard, 300 CPM card reader, 
300 LPM-136 column line printer and 4800 baud 
communications capability. Complete original 
service and operation documentation included. 
Excellent condition, currently under CDC main- 
tenance contract. Contact: Bob Levy or Bob Minor 
(301) 565-9544 8750 Georgia Av, Silver Spring 
MD 20910. 

FOR SALE: Motorola MEK6800O2 evaluation 
kit, 8 K Solid State Music Memory board. Includes 

4 slot Altair (S-100) extender board, cabinet, 

5 V 6 A power supply, Mik-Bug firmware, 8 K 
(SwTPC) BASIC, 8 K (SwTPC) Text Editor and 
Assembler, 4 K Tiny Assembler, PCC's BASIC 
games, (the evaluation module has an integral 
Key board /Cassette interface) and COMPLETE 
SYSTEMS/Family Documentation. Must sell! 
Asking $350 — will take best offer. Amn Trotz, 
Psc Box 1 1 16, Wurtsmith AFB Ml 48753. 

FOR SALE: Lunar Landing simulation program 
for any Radio Shack TRS-80 computer. On cas- 
sette, ready to load. Send check or money order 
for $7.50 to J Quistgaard, 715 S Alder St, Port 
Angeles WA 98362. 

FOR SALE: Heathkit H-9 video terminal, expertly 
assembled, $600. Also, box of ten 8 inch Data 
Packaging (DPI) floppy disks, never used, $50. I 
pay shipping, Andy Thornburg, 400 E Jackson St, 
DeSoto I L 62924. 

WANTED: Card extender or connector (male and 
female ELCO PNOO- 701 5-059-000-002) for DATA 
POINT 3300-101 59 pin. Cecil T Rutledge, 2726 
Sandy Ln. Fort Worth TX 761 1 2. 

FOR SALE: Altair 8800B computer with 32 K 
200 ns static programmable memory, two serial 
ports, one parallel port, PROM board, ACR 
cassette interface, floppy disk drive and con- 
troller, panel mounted baud rate switches for 
fast device change, extended BASIC on cassette, 
disk extended BASIC, and DOS, along with 30 
floppy disks. $5000, Steve Mastrianni, 2952 Mam 
St, Coventry CT 06238. (203) 742-6727 or (203) 
664-2401 . 

Apple II Software cassette: 16 K Blackjack mutli- 
color card display, 2 player paddle input, full 
Las Vegas rules, optional autoplay by computer, 
sound effects, documentation included, $10. 
George W Lee, 18803 S Christina Av, Cerritos 
CA 90701 . 

FOR SALE: All issues of BYTE from September 
1975 to August 1977. All issues completely 
intact and in mint condition. Best offer over $60 
within one month after ad's appearance. Richard 
Fermoyle, 7597 NW 73rd Ter, Tamarac FL 
33319. 

FOR SALE: One Compucotor 8001 color terminal 
with BASIC SOOT, background color option 32 K 
programmable memory (8 K for CRT), floppy 
tape bulk storage. CPU operating system includes 
memory manipulation and paper tape 10 sub- 
routines. One free serial 10 port. In perfect 
operating condition, $2995. Contact D Brovwi, 
(803) 771-6087, 1308 Shirley St. Columbia SC 
29202. 



206 July 1978 © BYTE Publicitions Inc 



VISIBLE 

OR 

INFRA RED 



USED FOR CHARACTER 

RECOGNITION FOR 

COMPUTERS WITH 

EXTERNAL CIRCUITS 



MAY BE USED IN 

A VACUUM, 
UNDER WATER, 
HIGH ALTITUDE 



IN MAGNETIC ENVIRONMENT 
BECAUSE THERE IS NO 

HIGH VOLTAGE OR 
MAGNETIC DEFLECTION 



MINATURE SOLID STATE 



202 VIDEO CAMERA KIT 

FEATURING A. . . 100 x 100 BIT SELF SCANNING CHARGED COUPLED DEVICE 



THIS UNIQUE UPDATED CAMERA KIT 

FEATURES THE FAIRCHILD CCD 202C IMAGE SENSOR 



ADVANTAGES 

• IN THE FUTURE 
WE WILL SUPPLY A 

COMPUTER VIDEO INTERFACE CARD 

• All clock voltages operate at 6V 
reguiring no adjustments 

• Higher video output signal 

• We supply the power board, so only 
a 5V 1 Amp power source is needed 

• The circuitry has been simplified for 
easier assembly 

• Two level TTL output is supplied for 
interfacing 



FEATURES 

• Sensitive to infra red 
as well as visible light 

• May be used for IR surveillance 
with an IR light source 

• Excellent for standard 
surveillance work, because 
of light weight and small size 

• All components mounted on 
parallel 33/4"x6V2" single 
sided boards 

• Total weight under 1 lb. 





SURPLUS CENTRONICS PRINTERS 



306 



'1,150 
*900 



^QdQoo ,.„ 

^^0^M ^^ IVI I We supply all semiconductors, 

... ^ . , _i X i boards, data sheets, diagrams. 

Add $75. ° to assemble and test resistors and capacitors, and 

SMM lens. 

Add $2.00 Postage and Handling sorry we do not supply the 

case, batteries and 5V supply. 



UNIVERSAL 4Kx8 MEMORY BOARD KIT 

$69.95 

32-2102-1 fully buffered, 16 address lines, on 
board decoding for any 4 oi 64 pages, standard 
44 pin buss, may be used with F-8 & KIM 

EXPANDABLE F8 CPU BOARD KIT 
$99.00 

featurint] Fairbug PSU 1 K-ot siaiic ram, RS 232 
interface, documentation. 64 BYTE teqis.er 

4K BASIC FOR FAIRBUG F8 

on naner rai>P $25 00 

C/MOS (DIODE CLAMPED) 

4001 ■■ IB 4016 - .29 4027 - 37 4053 -• 1.10 

4002- ,18 4017 - .90 4028- .80 4055- 1.25 

4006- .95 4018- .90 4029- .95 4066- 70 

4007 - .18 4019- 37 4030- 33 4071 - .18 

4009 • 37 4020 - .90 4036 - .97 4076 - .97 

4010- 3? 4021 .90 4042- .65 4518- 1.00 

4011 - .18 4022- 90 4046- 1.35 74C10 .22 

4012- .18 4023- .T8 4047- 150 74C193 .95 

4013- .29 4024- 75 4049- ,34 

4015 - .74 4025 ■ 18 4050 - 34 

2TO»HK ePROM 1460 nl) $ 9.75 

2622 STATIC SHIFT HE6 t 1.95 

2513 CHAHACTEH G6N t 6.7B 

2B1S HEX 32 BIT SR ..._ ., % 2.20 

5203-2K CPROM ^ S 4.60 

2102 1 (450ni) S .99 

21L02 1 USOnil S 1.26 

WM5370 4KXI DYN S 3.4S 

MK 40O8P ^ S 1.95 

2101 1 254 ■ 4 STATIC • 2.46 

2111 1-256 X 4 STATIC t 3.45 

2112 1 256 M 4 STATIC „ • 2.76 

S2B0/21D7e 4K DYNAMIC BAM .„.. t 4.36 

TMS 4060L , $ 3.96 

5204-4K "ROM _ „ S10.9& 

82S23 „ S 1.95 

AY 6-1013 UAHT ^ $ 6.96 

B703C TELE DYNE 3 STAGE 

eiNAHY a BIT A/D CONVERTER S13.SD 

90eOA . . «H.95 

AP SOARD5 USED FOR 
50LDERLCSS BREADBOAR Dl NG 
264L - 128 FIVE-TIE POINT ,,„ cr, 

TERMINALS $12.50 

212H —POWER BOARD $ 2.50 

2248L- 96 FIVE TIE POINT *, „ „„ 

TERMINALS $10.00 

209R - POWER BOARD $ 2.25 

IC TEST CLIPS 
TC-1^~ S4.S0 TC-16 - t4-75 

CTS 206-8 ei9hi position dip switch .... $1.90 

CTS-206-4 tour position dip swuch . . . .Si.45 
LIGHT ACTIVATED SCR'j 
TO 18. 200V 1A $ 1.10 

SILICON SOLAR CELLS 
2%" diametef .4V at 500 ma $4.00 

FND 359C.C..4"$.50 LED READOUTS 

FCS8024 4 digit DL-704C.A. .3" $ .85 

C.C. 8" airplay $5.95 DL747C.A. ,6- $1.65 

FND 503 C.C, ,5" $ .85 FND 800 C.C. ,8" $1.95 

FND 510 C.A. .5" $ .85 FND 807 C.A. ,8" $1.95 
DL 704 .3" C.C. $ .85 



PRINTED CIRCUIT BOARD 



7WATTLD 65 LASER DIODE I R $a95 



2N 3820 P FET S 45 

2N 5457 N FET $ 45 

2N2646 UJT $45 

ER 900 TRIGGER DIODES 4' SI. 00 

2N 6028 PROG UJT S 65 

MINIATURE MULTI-TURN TRIM POTS 
100, IK, 2K, 5K, 10K. 25K, 50K, TOOK, 
200^:. 500K. IMeg, 2Meg, $.75 each 3/$2.Q0 

CHARGED COUPLE DEVICES 
CCD 321 AH2 512 Analog Shiit Register . $95.00 

CCD201C 100x100 Image Sensor $95.00 

CCD 202C 100x100 Imago Sensor $145.00 

VERIPAXPC BOARD $4.00 

This board is a 1/16"singla sided paper epoxy 
board, 4>'j"x6%" DRILLF.D and ETCHED which 
will hold up to 21 single 14 pin IC's or 8,16 or LSI 
DIP IC's with busses for power supply connactor, 

FP 100 PHOTO TRANS . . . S 50 

RED, YELLOW. GREEN or AMBER 

LARGE LED's .2" ... 6/$1 00 

TIL-nS OPTO-ISOLATOR $ .75 

MOLEX PINS 100/$]. 00 

1 ooa/$8 00 

10 WATT ZENERS 3.9. 4.7. 5.6. 8.2, 

18,22,100,150 or 200V , ea. $ .60 

1 WATT ZENERS 4.7, 5.6,10. 12. 15 

18 or 22V ea. S .25 

MC6860 MODEM CHIP $9.95 

MCM6571A 7x 9characiergen ... $10.75 



TRANSISTOR SPECIALS 

2N6233-NPN SWITCHING POWER $ 1-95 
MRF-8(»4a CB RF Transistor NPN $ 1-50 

2N3772 NPN Si TO-3 . $ TOO 

2N1546 PNP GE TO-3 $ .75 

2N4008 PNP yi TO :i S 1 00 

2N6056 MPIM Si TO 3 D,iihniHo-i S 1.70 
2N5086 PNPSi TO-92 . . . 4/S 1.00 

2N3137 NpN Si RF $ .85 

2N3919 NPN Si TO 3 RF . --. SI 50 

2N1420NPNSiTO54 3/$ 1.00 

2N3767 NPN Si TO-66 ... S .70 

2N2222 NPN Si T018 . . , 5/S 1 00 

2N3055 NPN Si TO 3 ... S .50 

2N3904 NPN Si TO-92 . 5/S 1 .00 

2N3906 PNP Si T0 92 . . . 5'S 1.00 

2N5296 NPN Si TO-220 S .50 

2IM6109 PNP Si TO-220. ... S .55 

2N3638 PNP Si TO 5 5/S 1.00' 



^SESEMS 



600 



.20 



».oo 



DIP SOCKETS 

B PIN .17 24 PIN .35 

14 PIN .20 28 PIN .40 

16 PIN ,22 40 PIN .60 

18 PIN .25 



5ANKEN AUDIO POWER AMPS 

Si 1010 G 10 WATTS. ... $ 7.80 

Si 1020 G 20 WATTS ' . . $15.70 

Si 1050 G 50 WATTS $28.50 



TANTULUM CAPACITORS 



TTL IC SERIES 



Silicon Power Rectifiers 



PRV 1 A 3A 12A 50A 1 ^■fA 241;A 

100 06 .14 .30 .80 3 70 s.qq 

200 07 .20 .35 1 IS 4.25 6.^0 

400 09 25 50 1.40 6.50 9.50 

600 11 .30 .70 1 80 8.5Q 12.50 

BOO 15 ,35 .90 2.30 10 50 16,50 

1000 20 .45 1.10 2 75 12 50 20.00 
SAD 1024-B REDICON 1024 stage analog "Bucket 

B-^iaade" shift regiitar. $16.95 

IN 4148 MN914I 15, Si 00 

RS232 DB 25P male $2.95 

CONNECTORS D6 ^5S female ... $3.50 

REGULATORS 

309K $ ,95 340K 12,15 

723 S .50 Of 24V. .... $ .95 

LM 376 .... $ -60 340T 5, 6, 8, 12 
320K 5, 12 15.18 or 24V $ .95 

or 15V. .. $1-00 78 MG $1.35 

'°Ir^2-4V,... $ .95 ^^ MG $1.35 



7400- 


.13 


7445- 


,65 


74151- 


7401- 


.13 


7446- 


.68 


74153- 


7402- 


.13 


7447- 


.58 


74154- 


7403- 


.13 


7448- 


.68 


74155- 


7404- 


.15 


7450- 


.15 


74157- 


7405- 


-13 


7472- 




74161- 


7406- 


-16 


7473- 


.28 


74163- 


7407- 


,20 


7474- 


.28 


74164- 


7408- 


.18 


7475- 


.45 


74165- 


7409- 


.18 


7476- 


.30 


74170- 


7410- 


.13 


7480- 


.31 


74173- 


7411- 


IB 


7483- 


.65 


74174- 


7412- 


.13 


7485- 


.87 


74175- 


7413- 


.36 


7486- 


.28 


74176- 


7414- 


.60 


7490- 


,42 


74177- 


7416- 


.22 


7491- 


.58 


74180- 


7417- 


.25 


7492- 


.43 


74181- 


7420- 


.13 


7493- 


.43 


74190- 


7425- 


25 


7494- 


.67 


74191- 


7426- 


.22 


7495- 


.65 


74192- 


7427- 


,19 


7496- 


.65 


74193- 


7430- 


.13 


74107- 


,28 


74194- 


7432- 


.22 


74121- 




75325- 


7437- 


.21 


74122- 


38 


74196- 


7438* 


.21 


74123- 


,45 


74279- 


7440- 


.13 


74125- 


.40 


74367- 


7441- 


.70' 


74126- 


40 


75491- 


7442- 


.37 


74150- 


.94 


75492- 




DATA CASSETTES 


$ 



44 Pin Solder Tail .156" Conn. 



IVIM 5387AA new clock chip which v 
drive LED's 1 2/24 hrs., 1 supply & al 



NO. 30 WIRE WRAP WIRE SINGLE 
STRAND 100' $1.40 



22UF 35V 5/Sl.OO 
47UF 35V 5/S1 00 
68UF 35V 5.S1 00 
1UF 35V 5,S1 00 

2 2 UF 20V5'S1 00 

3 3UF 35V 4 S1 00 
4.7UF 15V 5,'$1.00 



6 8UF 35V 4.S1 00 

lOUF 10V $ .25 

22UF 25V S 40 

15UF 35V 3/$l,00 

30UF 6V 5/$1.00 

47UF 20V $ .35 

68UF 15V $ .50 



LINEAR CIRCUITS" 



LM30a 
LM311 
LM31S 
LU319 
LM324 
LM339 
LU 358 
LM 370 



- 1,26 
-2.50 
-2-50 



ALCO MINIATURE TOGGLE SWITCHES 
MIA 106 SPOT . .... $ 1.05 

MTA 206 DPDT S 1.70 

MTA 206 P-DPDT CENTER OFF « i 85 

MSD 206 P-DPDT CENTER OFF 

LEVER SWITCH $ 1.85 




Circle 340 on inquiry card. 



BYTEluly]978 207 



Feadep Service 



To get further information on the products advertised in BYTE, fill out the reader service card with your name and address. Then circle the 
appropriate numbers for the advertisers you select from the list. Add a 13 cent stamp to the card, then drop it in the mail. Not only do you 
gain information, but our advertisers are encouraged to use the marketplace provided by BYTE. This helps us bring you a bigger BYTE. 



Inquiry No. Page No. 

4 Administrative Systems 1 14 
AJA Software 135 
Anderson Jacobson 45 
Apple Computer 14 
Apple Computer 15 
AVR Electronics 159 
ATV Research 133 
Atwood Enterprises 180 
Beckian Enterprises 180 
Bit Basement 137 
BITS82, 83, 87, 110, 133 
Buss 112 

BYTE Back Issues 146 
BYTE Wats Line 103 
California Industrial 185 
Canada Systems 143 
Capitol Equipment Brokers 126 
Carterfone 161 
Central Data Corp 103 
Component Sales 183 
Computer Data Directory 110 
Computer Enterprises 106 
Computer Headware 1 1 1 
Computerland 33 
Computer Mart of MA 1 59 
Computer Mart of NJ 144 
Computer Mart of PA 144 
Computer Resources 159 
Creative Software 159 
Cromemco 1 , 2 
T Y Crowell 120 
Cybernetic Micro Systems 131 
Databyte 123 

Digital Equipment Corp 172 
Digital Group 19 
Digital Research (CA) 143 
Digital Research (TX) 187 
Digital Research & Engineering 111 
Dynabyte 67 
ECHOlab Inc 110 
Electrolabs 183 

Electronic Control Technology 141 
Electronic Systems 189 
Electronics Warehouse 191 
EMM/CMP 118 
EMM/Semi Inc 109 
Engram Associates Inc 131 
Forethought Products 126 
Gallaher Research Inc 129 
* GFN Industries Inc 79 
148 GRT Corporation 22, 23 



6 
10 
14 
15 
16 
17 
25 
30 
31 
35 
36 



39 
40 
43 
84 
45 
60 
61 
70 
73 
75 
74 
76 
76 
77 
78 
80 
81 
82 



90 
95 
100 
101 
110 
113 
115 
120 
125 
130 
132 
136 
137 
140 
145 



Inquiry No. Page No. 

149 H & K Computer Corp 140 

153 Hamilton Logic Systems 159 

155 DC Hayes 119 

160 Heath Company CIV, 34 

170 Hobby World 1 79 

175 IMSAICIII 

178 Info 2000 69 

73 Information Unlimited 11 1 

179 Integrand 140 

180 Integrated Circuits Unlimited 193 
183 International Data Sciences 129 
185 International Data Systems 104 

187 International Technical Systems Inc 159 

190 Ithaca Audio 161 

193 J & E Electronics 133 

195 Jade Company 181 

200 Jameco Electronics 194, 195 

202 Kel-Amlnc144 

207 LMN Electronics 197 

215 Logical Services 173 

216 Magnemedia 99 

217 Manchester Equipment 137 
219 McGraw Hill Publishing 75 
223 Microcompl59 

226 Micro Computer Devices 109 

231 Micro Mart 137 

235 Micropolis96 

236 Micropolis97 
240 Microware150 
247 Mikos 198 

250 Mini Micro Mart 173 

251 Mini Micro Mart 199 
260 Mountain Hardware 5 
265 mpi 127 

* MVT Microcomputer Systems 147 

273 National Digital Diagnostic 133 

275 National Multiplex 73 

280 Netronicsl21 

283 Newman Computer Exchange 146 

285 North Star Computer 7, 21 

287 Northwest Microcomputing Sys 169 

290 Ohio Scientific Instruments 24, 25, 26, 27 
289 OK Machines Tool 113 

291 Oliver Advanced Engineering 135 

292 Oliver Advanced Engineering 137 

293 Osborne & Associates 93 

294 Pacific Digital 136 

296 Pacific Office Systems 198 

297 Page Digital 188 

298 PAIA Electronics 108 

299 Pentech Inc 137 



Inquiry No. 



Page No. 



301 PerCom Data 29 

302 Personal Computing '78 81, 151 

* PolyMorphic Systems 13 

303 Poly Paks 203 

304 Priority I Electronics 201 

305 Processor Technology 8, 9, 10 

306 Quantum Science Corp 159 

307 Quest Electronics 188 

308 Rothenberg Information 115 

309 Rotundra Cybernetics 137 

311 S-100 108 

310 ScelbiSO, 31 

322 Scelbi/BYTE Primer 95 

* Scientific Research 47, 49 

312 Scope Data 133 

31 5 SD Computer Products 205 

313 Seattle Computer Products 105 

314 Sherwood Medical 133 

316 Michael Shrayer Software 77 

317 Siliconix 59 

318 Small Systems Services 147 

319 Ed Smith's Software 128 

320 Smoke Signal Broadcasting 107 

321 Smoke Signal Broadcasting 128 
330 Software Records 136 

335 Solid State Music 11 

340 Solid State Sales 207 

350 Southwest Technical Products CM 

351 Structured Systems Group 17 

352 Summagraphics Inc 122 

353 Super Surplus Sales 204 

355 Synchro Sound 39 

356 Synchro Sound 40, 41 
360 Tarbell Electronics 43 

370 Technical Systems Consultants 37 

372 Technico 65 

373 Technicon 117 

371 Teletek Enterprises 137 

374 Terrapin Inc 71 

376 Touchstone Associates 137 

377 Transition Enterprises 159 

378 TransNet Corp 127 
381 Tri Tek 204 

383 TRS-80 Software Exchange 141 

386 US Robotics 137 

388 Vandenberg Data Products 142 

393 West Coast Computer Faire 51 

395 Worldwide Electronics 133 

400 Xitexl16 

405 Xybek 142 

*Correspond directly with company. 



mm- 

BYTE's Cdgcing Moflifon Bex 



Article No. 

1 

2 

3 

4 

5 

6 

7 

8 

9 
10 
11 
12 
13 



ARTICLE 



Baker: KIMER: A KIM-1 Timer 

Bosen: The Axiom EX800 Printer: A User's Report 

Hearn: Top-Down Modular Programming 

Hauck: Who's Afraid of Dynamic Memories? 

Williams: Antique Mechanical Computers: Early Automata 

Loewer: The Z-80 in Parallel 

Libes: The First Ten Years of Amateur Computing 

Walton: Controlling DC Motors 

Reid-Green: A Short History of Computing 

Ciarcia: Build a Keyboard Function Decoder 

Frenzel: How to Choose a Microprocessor 

Williams-Conley: A High Level Language for 8 Bit Machines 

Weinstein: How to Get Your Tarbell Going 



PAGE 

12 

28 

32 

42 

48 

60 

64 

72 

84 

98 

124 

152 

162 



Readers Tune In to Ciarcia 

The winner of the April BOMB is Steve 
Ciarcia's "Tune In and Turn On: A Com- 
puterized Wireless AC Control System, Part 
1," page 114. Second prize goes to Ernest 
W Kent's "The Brains of Men and Machines, 
Part 4: The Machinery of Emotion and 
Choice," page 66. The authors will receive 
prizes of $100 and $50, respectively. 

The BOMB (BYTE's Ongoing Monitor 
Box) is your way of telling us what you 
think about the articles in BYTE each 
month. To cast your votes, see the card on 
the opposite page." 



208 luly 1978 © BYTE Publications Inc 



icrocomputer 
System Solution. 

Announcing thelMSAI VDP'40. 






Fully integrated video data processor in a 
single cabinet. 

T\vin floppies, professional keyboard, 
S-100 expansion slots. 
24 line by 80 char. CRT, insert/delete, 
programmable font, protected fields, 
inverse video. 

Handsome flip-top cabinet for easy access. 
Serial and parallel I/O ports included. 
FORTRAN IV, Extended and Com- 
mercial BASIC. 

IMDOS (enhanced CP/M*). r rj 

ISAM. . "f r fft: 



-ffrr 





You've decided you want a microcomputer 
system — but what to buy? The component 
system? A computer lx)x here, a CRT lx)x 
there, a keyboard box here, a floppy disk 
box there . . . Messy! The $695 system? But 
... no disk; no way to add enough memory 
. . . and, if you could, it's not so cheap 
anymore, and you still wind up with an 
expensive box collection anyway. Messy! 

The IMSAI VDP-40, a fully integrated 
Video Data Processing system that, in one 
handsome package, combines a profes- 
sional keyboard, heavy-duty power supply, 
twin mini-floppies, multi-slotted mother- 
board and 9-inch CRT at a new low price. 

System Expansion? The IMSAI VDP-40 
was built for you. The extra slots in our 



S-100 bus motherboard 
and heavy-duty power supply 
allow almost unlimited expansion. 
Need more RAM? Add up to V2 MByte 
with our Intelligent Memory Manager and 
64K RAM boards. Need more disk storage? 
A controller option of the VDP-40 will 
allow you to expand to nearly 5 megabytes! 
Add a line printer, an IBM-compatible tape 
drive, a MODEM! IMSAI has them all, 
with the interfaces and software to make it 
work for you. The standard of excellence 
IMSAI places at your disposal at a price/ 
performance no one else has put together 
allows you to achieve the full potential of 
your imagination. 



Check us out. 
IMSAI has what you want 
and what you need. Visit your dealer 
or write us directly. Ask about the IMSAI 
VDP-40 and the entire IMSAI line. 

Features and prices subject to change without notice. 
* CP/M is a trademark of Digital Research Corporation. 





The Standard of Excellence 
in Microcomputer Systems 

IMSAI Manufacturing Corporation, 
Dept. EWN, 14860 Wicks Boulevard, 
San Leandro, CA 94577 (415) 483-2093 



IMSAI EUROPE Europa Terrassen 8 Rue Jean Engling Dommeldange, Luxembourg 43-67-46 Telex: 1428 

See us at the NCC Show, booth 2860 

Price/Performance no one else has put together. 

Circle 175 on inquiry card. 



This 8-bit machine, 

by itself, is as versatile 

as a lot of systems 

that include peripherals 



orientation allows you an almost 
unlimited opportunity for growth. 

Memory is fully expandable, the 
8080A CPU extremely versatile, and 
with the addition of high speed serial 
and parallel interfacing you gain 
the added flexibility of I/O operation 
with tape, CKT consoles, paper 
tape reader/punches, and now our 
new floppy disk systems! 

The H8 offers superior documen- 
tation including complete step-by- 
step assembly and operation 
manuals, is backed by 54 years of 
Heath reliability, and comes 
complete with BASIC, assembler, 
editor, and debug software - 
others charge over $60 for! 

H8, simplicity for the 
beginner, sophisti- 
lation for the expert 
nd at $375* just rigt 
r you. 




the H8 is the 
only machine 
in its price 
class that 
offers full 
system inte- 
gration yet, 
with just 4K of 
optional mem- 
ory and using 



I/O Port Display 



System Engineered 
for Personal Computing 



Be sure to use coupon on 

page 34 of this magazine 

to order your FREE 

Heathkit Catalog! 




only its "intelligent" 

front panel for I/O, may be operate 

completely without peripherals! 

In addition, by using the features of 
its built-in Pam-8 ROM panel 
control program, the H8 actually 
allows you to dig in and examine 
machine level circuitry. 

Responding to simple instructions 
the "intelligent" panel displays 
memory and register contents, lets 
you inspect and alter them even 
during operation. And for greater 
understanding, the front panel 
permits you to execute programs a 
single instruction at a time. The 
result is a powerful, flexible learn- 
ing tool that actually lets you "see" 
and confirm each detail of H8's 
inner workings. 

If you need further evidence, con- 
sider the fact that H8's system 




U- 



Circle 160 on inquiry card.